Model Boat Mayhem
Mess Deck: General Section => Chit-Chat => Topic started by: hopeitfloats on May 24, 2011, 10:11:48 am
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what does 10 + 10 x 0 = . on another message board there were 2 likely answers. 10 or 0. any thoughts.
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BODMAS
http://www.mathsisfun.com/operation-order-bodmas.html
in which case the answer is 10
Nick
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Try the concept:
ANY number multiplied by zero equals ZERO
Regards.
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thats how i was taught to but apparently the answer is 10 . maths has obviously changed since the 60's/70's.
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thats how i was taught to but apparently the answer is 10 . maths has obviously changed since the 60's/70's.
How do you get to that?
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Is it (10 + 10) x 0 = 0
or is it 10 + (10 x 0) = 10
Before the days of parentheses there were rules about what operator was used first. I think the rules may still apply to computers and some calculators.
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A form of maths illusion?
Written out as it should be considered it would be:
10 + (10x0) which would be 10 + 0 = 10
Most people ( :o) have read this "as is" : 10+ 10x0 = 20x0 = 0
DOH (to myself)
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As the question is written 10 + 10 x 0 then it should be 0.
If the answer is 10 then its a badly written question!
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As the question is written 10 + 10 x 0 then it should be 0.
If the answer is 10 then its a badly written question!
If you work from left to right and do each piece as you go, then yes.
But I think there are a hierarchies of operators. Like x out trumps /, / out trumps +, and + out trumps -. (not sure of the exact order BTW)
In this case you would do the multiplication bits first, then the plus bits.
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thats the answer i was given. multiplication first then addition. parenthesis means nothing nowdays.
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Copied from the link. Important words below "long ago'
And even now bracketrs first.
"Operations" mean things like add, subtract, multiply, divide, squaring, etc. If it isn't a number it is probably an operation.
But, when you see something like...
7 + (6 × 52 + 3)
... what part should you calculate first?
Start at the left and go to the right?
Or go from right to left?
Calculate them in the wrong order, and you will get a wrong answer !
So, long ago people agreed to follow rules when doing calculations, and they are:
Order of Operations
Do things in Brackets First. Example:
6 × (5 + 3) = 6 × 8 =
48
6 × (5 + 3) = 30 + 3 =
33
(wrong)
Exponents (Powers, Roots) before Multiply, Divide, Add or Subtract. Example:
5 × 22 = 5 × 4 =
20
5 × 22 = 102 =
100
(wrong)
Multiply or Divide before you Add or Subtract. Example:
2 + 5 × 3 = 2 + 15 =
17
2 + 5 × 3 = 7 × 3 =
21
(wrong)
Otherwise just go left to right. Example:
30 ÷ 5 × 3 = 6 × 3 =
18
30 ÷ 5 × 3 = 30 ÷ 15 =
2
(wrong)
How Do I Remember It All ... ? BODMAS !
B
Brackets first
O
Orders (ie Powers and Square Roots, etc.)
DM
Division and Multiplication (left-to-right)
AS
Addition and Subtraction (left-to-right)
Divide and Multiply rank equally (and go left to right).
Add and Subtract rank equally (and go left to right)
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Tiger Tiger is correct about the calculation sequence in computers, without parenthesis (or brackets as I was taught) a computer will use, left to right, multiplication and division then addition and subtraction. With brackets, the rule is inside the brackets first, again left to right. Brackets within brackets, then the order is inside out.
In the absence of brackets I would use the left to right rule, as does my calculator.
However, I was also taught :
There is no such thing as a bad answer only a bad question. (Not to sure about that though)
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Interesting
Where do you go with ; root 3 E I cos Theter???? Sorry computer doesnt have correct symbols. :-)
Glen
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we use http://www.wolframalpha.com/ where i work for definitive answers which comes out at 10. as others have said its the way its written
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Intrigued by this I have just consulted my son, whose education was far more recent than mine (he's 23). He was taught brackets first, then multiplication and division, then addition and subtraction. That is how a computer does it. However, when I teach the over 50s to use computers I always point out the order of calculation they use and have never met anyone who has not expressed surprise. Another subtle change to bite you in the rear end when you're not looking. >>:-(
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just done a course on this to help my daughters at school. and it is a case of BIDMAS or BODMAS THEORY that takes over riding mechanical maths, and all to do with the way modern scientific calculators are programmed.
the answer is................ 10.
10 +( 10 divided by 0 )
multiplication takes preference over division which takes preference over subtraction then addition, and scientific calculaters calculate the answer in that order. tyhat is, unless you insert your [ ] ,( ) which then changes the order of calculation
neil.
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My head hurts :o
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multiplication takes preference over division which takes preference over subtraction then addition, and scientific calculaters calculate the answer in that order. tyhat is, unless you insert your [ ] ,( ) which then changes the order of calculation
neil.
Are you sure? That's not what computers do. They take Division and Multiplication first but in the order they are met left to right, then the same with addition and subtraction. So
10/4*5 = 12.5 not 0.5
Going to have a long lie down now
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Are you sure? That's not what computers do. They take Division and Multiplication first but in the order they are met left to right, then the same with addition and subtraction. So
10/4*5 = 12.5 not 0.5
Going to have a long lie down now
NO!, Dougal, not sure at all.......and in fact had a discussion with the lecturer about it that took up almost a full session......but that's what she insisted was correct...........so, who am i but to do and die. lol................i'm no more sure than you are, and that's what i find confusing....that an electronic device can change and dictate all mathematical process that i as a kid, and for years taught to other kids, just because some boffin has decree'd that it should be............i'll stick to my simultaneous equations, thank you, lol %% %% %% %% %% %%
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nhp651
whilst its a mild irritation to me not so for you. I would want it absolutely clarified for my child. Exams, like it or not, are getting more and more important in deciding where our child's future may lie. The website in one of the earlier posts, agrees with my interpretation, whilst that's not conclusive it does raise doubt over your tutor's interpretation. Have you got some examples with answers or can you get some?
Good luck
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It is perhaps worth pointing out here, that we are taught by the rule of diminishing errors.
What you teach primary school kids is not as precise as what we teach middle school kids. When we get to high school we learn that some of the things taught in primary school were perhaps inaccurate to the point of being flawed. But how do you teach a child some higher level knowledge without teaching them some basics that they can comprehend.
When we go to university you discover how little we are actually taught at high school and we learn to challenge accepted 'knowledge', that we had once accepted as absolute.
The maths I use is technically flawed, but it meets my needs. However, if I was studying computer science at a higher level, what I know will not meet all cases.
And so we have the dilemma about what do we teach.
An example of the rule of diminishing errors.
I was initially taught that the basic building block of the universe (the smallest thing) was an atom.
I was latter taught that in fact the atom is made up of electrons, protons, and neutrons. I was also taught that in most cases we don't get single atoms, but molecules.
I was then taught about sub-atomic particles.
For my life I don't need to think at the micro level, but at the macro level.
For example, if I don't clean my boat off after it has been in the sea, bits go rusty, or corrode and my boat won't work.
Or if I leave things in the sun they can degrade due to UV light.
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Quick point on exams.
If the syllabus says that the moon is made of cheese. Then that is what you need to write in the exam if they ask "What is the moon made of?"
We are tested on the syllabus up to high-school level.
In science we are not tested on our knowledge of science, but on our knowledge of the science syllabus we were taught. Same for all subjects.
And as such you can relax Dougal. The website you posted was for primary and secondary school maths.
What nhp651 was describing was (if I am right) tertiary level maths. Something your child will not have to worry about for a while yet.
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Picked up desk calculator, keyed in the sum EXACTLY as quoted in the first post, the answer is 0.
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From what I was taught, the sequence to calculate numeracy is:
Brackets or Divide, Multiply, Add and Subtract (BODMAS)
therefore,
10 + 10 x 0
10 + (10 x 0)
10 + 0
10
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There are no brackets (--) in the original question though?
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Tiger tiger
I'm relaxed all my children are grown up and my homework helping days are over. However, others with schoolkids are being taught the 'new' methods so they can help their children. If that teaching is flawed the help is a disadvantage not an advantage. Your law of diminishing errors does not work if the teaching at one level is flatly contradicted at a later level. It matters whether you do division or multiplication first so the rule must be consistent whether in primary school or at university. Any given calculation must have the same result whenever you perform it, otherwise mayhem!
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i the real world tho who the hell does a sum and multiplys by 0
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AHHHH !
My head is going to explode,just spent an hour or so going through,the maths coursework for my plumbing course.
Now remember i left school in 1979 and never could work out pie,volumes,masses and the rest of it.
Come on to see about boats,and see more maths {-)
Mark
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i the real world tho who the hell does a sum and multiplys by 0
I'm sure that sum do! :embarrassed:
Worse still are those that divide by 0! {:-{
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Last year Martin gave us moderators a 10% pay rise. :-))
0 x 110% = 0
He did, honestly. :-)
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to make the answer 0 the equasion would have to be
(10 +10) x 0 = 0
Nick
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From what I was taught, the sequence to calculate numeracy is:
Brackets or Divide, Multiply, Add and Subtract (BODMAS)
therefore,
10 + 10 x 0
10 + (10 x 0)
10 + 0
10
As Kleban has said, BOMDAS is the world wide mathematical principle (was when I did school 60/70s). IF there are no brackets, then do all the dividing and multipling, then and only then start adding and then subtracting. It is a simple principle. It does not follow english language principles of left to right.
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I was in school up until 1967 and BODMAS was definitely not taught to me. Unless there were brackets, you moved left to right. I suspect the advent of scientific calculators, and their use in schools caused the change. When I was in the sixth form we had a real 'monk on' when we found that the fourths were using slide rules!
Technology. Don't you just love it?
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It's really quite disturbing to see so many not only do something so simple incorrectly, but clucking like chickens about "That's not how I was taught!"
The order of operations for solving math problems has been around longer than anyone on this forum's been on Earth - it's nothing new.
I imagine fellows like Camping went to the same schools, which is why he can't figure out the right date for the end of the world.
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Jeez!, aint half glad my life don't depend on any of this! {-) {-) {-)
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Hey
I got as far as the end of TigerTigers post and I thought hey - I actually get it and give Tiger a prize! I read on, lost the will to live, and have opened the magic mead again - soon everything will make perfect sense again.
Regards Norseman
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Its funny what you were taught at school. I always loved English Language but cared little for the difference between a pronoun and a preposition. They were terms to describe something I would be using, but I felt it was more important to concentrate on the meaning and use of the words. This, and the correct use of punctuation, have been of more use to me throughout my life, than the fancy names given to words.
It was a similar situation with maths. Ok, I have occasionally had the need to use some trigonometry, and possible even basic algebra, but a great deal of what I learned has been completely useless. For example, I have never felt an overwhelming desire to find out the height of some landmark or other with the aid of a protractor. I could look it up in Encylopedia Brittanica - or even easier nowadays, "Google" it!
As for quadratic equations ...
The modern generation may have the technological advantage over me, but when I see the level of basic education, I cringe!
Btw (see, I'm not a complete Luddite) has anyone ever found a use for negative numbers? I certainly haven't, unless you include my 'shopping' costs when being relayed to my dearest!
Cheers
Danny
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Ok the magic mead is working now, things are getting clear
Negative numbers are everywhere from the balance sheet to the weather man to electronics. What is more mind blowing is some guy a few hundred years ago has some magic mead and starts pondering the possibility of a square root of minus 1 - down in the shed where he can get out of the earshot. This gets forgotten/ rediscovered and we end up with the imaginary number i. Next thing you know the maths guys have engineers making sat navs and computing impossibley difficult stuff using i. Marvelous thing maths - I'm glad someone understands it.
Regards Norseman
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0 - either using a computer or using the noddle. No brackets means calculate from left to right and, as any fule kno, when you multiply anything by zero, the result is zero. i.e. 10 carrots + 10 carrots = 20 carrots, but 20 carrots times nothing is nothing. Simples *squeak*
Oh, and there is no such thing as minus numbers. I just drove 50 miles in my car and my petrol gauge dropped a few notches, so I drove back again, -50 miles, but my petrol tank didn't fill itself up again. I'd like 10 carrots please - why can't you give me -10 carrots? Because you're not mathematician and this is an underrtakers? Ok thanks very much, I'll go and see if the doctor can help. NUUUURSE. the screens , please!
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I'll put a sheep station on it...................... :embarrassed:
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Multiply or Divide before you Add or Subtract. Example:
yes 2 + 5 × 3 = 2 + 15 = 17
no 2 + 5 × 3 = 7 × 3 = 21 (wrong)
Its exactlythe same equation <*<
Straight from the link I posted >>:-(
Nick
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:(( {:-{ mmmm
Some time ago I was listening to my eldest daughters partner [university graduate] talking about negative equity <:( now I had studied a little economics @ the University of Wollongong light years ago.....but did not recall this term when associated with a motor vehicle
How silly could I be {-)...it simply means he owes more money $ in continued lease repayments that the vehicle is worth
So does this constitute a negative number? ........Derek
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At high school I was taught 10 + 10 x 0 = 0
Then I went to further education & was taught 10 + 10 x 0 =10
After further education I wen to the university of life & that taught me that life's to short to worry about it %%
cheers Glenn
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:(( {:-{ mmmm
Some time ago I was listening to my eldest daughters partner [university graduate] talking about negative equity <:( now I had studied a little economics @ the University of Wollongong light years ago.....but did not recall this term when associated with a motor vehicle
How silly could I be {-)...it simply means he owes more money $ in continued lease repayments that the vehicle is worth
So does this constitute a negative number? ........Derek
It is not a negative number.
If you default someone will come after you for the balance, I am positive about that.
%) %)
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Just wondering that with all the positves and negatives whether this question should be moved to Electrical, batteries etc
%) %) %) {-) {-) {-)
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Ah!
That reminds me of another one of those rules of diminishing errors.
In middle school physics, up to grade 10, we were taught basic circuits. We were told that electricity flows from positive to negative, and used this assumption in circuit diagrams.
However, in high school (grade 11-12) we were told that actually electricity is the flow of electrons. Therefore the flow of electicity is from the negative terminal towards the positive (in a DC circuit).
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Very impressive, Tiger! You obviously know your beans. There you are, giving the impression that you're just a humble model boat builder, yet you're actually a living, breathing mine of information.
Back in the days of Mssrs Ohm, Faraday, Hertz, et al, it was widely accepted that the direction of current flow was always emitted from the Anode (positive) terminal and to end up at the Cathode (negative) terminal. That was the convention of the day, hence the phrase "conventional current flow" was coined. Of course, we now know that the opposite is true, that electron current actually flows from negative to positive - otherwise called "electron current flow". An example of proof can be seen when we suffer that so-called dreaded "black wire" syndrome on our R/C battery connections.
Oddly enough, and quirky as we humans are, we still quaintly refer to current flow in the conventional sense.
And so end'eth today's history lesson #257b.
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Hi PMK, I did not know that electron flow was the reason for the black wire problem. I have just been changing plugs on a servo and have a wire gone black all the way down about 4 inches of it.
Are all negative wires on our RC destined to go this way?
I have been using RC since 1957 and have only found a few wires in this condition. I would appreciate a technical reason for it, or better still a solution.
regards Roy
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. Of course, we now know that the opposite is true, that electron current actually flows from negative to positive - otherwise called "electron current flow". And so end'eth today's history lesson #257b.
I don't doubt this for a minute - but why then are we told to put a fuse between the POSITIVE battery terminal and a motor ?
Don B
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Don: Because it harps back to those days when conventional current was considered the done deal. The positive (Anode) is still considered the so-called "hot" connection (even more so in AC circuits), so fuses by convention are placed in series with the positive rail. Also, bear in mind that in most modern circuits the negative is mostly always tied to ground in one way or another. The negative connection of, say, your R/C reciever will also be tied to the negative, of, say, your servos... and your ESC and your LEDs, etc. So it makes sense to fuse the positive side only.
Incidentally, most folk, when measuring the current in their circuits, will mostly always connect their ammeter in series with the positive rail. Did you know that you will get a much truer reading of the total current draw if the ammeter is connected in series with the negative rail? A thousand Green Shield stamps to you if you can tell me the reason why.
Roy: Black wire syndrom is basically a chemical reaction of the negative copper wire coming into contact with air. It's even more noticable when the air itself is humid or damp - a form of electrolyosis, very similar to how tin plating works. Try placing a copper probe and a zinc or stainless steel probe in a solution of acidic/salt water, then connect both probes to a DC supply. After a while you will begin to see the aforementioned chemical reaction taking place in the form of bubbles collecting around the probe which is connected to the supply negative probe - not the positive probe.
The general advice for R/C modellers is to not store their models in a cold, damp shed. If you must store your models in a damp environment, then a simple prevention of black wire syndrome is to disconnect the battery/batteries altogether. Better still, it's recommended to remove the batteries from the model during the Winter months and keep them in a room at normal ambient temperature.
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Further to PMK, any exposed metal bits, if they are connected to any part of the supply, will be connected to battery -ve. As an accidental grounding of a live wire is most likely to find one of these, the protection needs to be in the supply, i.e. +ve.
If the installation consists of several parts, having the -ve common and fusing the distribution makes sense. If it just a battery, receiver, ESC and servo, it still makes sense to put the fuse where it is conventionally expected, in the +ve side. This after 30 odd years in an industry where equipment was run on -50volts, and all the fuses were in the -ve supply, obviously apart from the +50volt supply........
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Thanks PMK, thank you for your thoughts. My shed is however nicely insulated and double glazed, it must be the house causing the problem.
Explanation is the best I have heard so will accept it.
Now what about the green stuff where the batteries go which is only ever at one end!
OK, I do take my batteries out now when not in use.
regards Roy
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Now what about the green stuff where the batteries go which is only ever at one end!
Verdigris. A copper compound, comes about where the terminals have become damp. Being used in a damp atmosphere, they will be damp long enough for the reaction to start taking place. The damp allows the reaction, extracting the copper, the compound spreads in the damp, the damp dries out and leaves the compound. Since boats operate in a damp environment, its going to happen.
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In the case of SLA batteries with spade-type terminals, I usually apply a generous dollop of petroleum jelly to both connections in order to keep that unwanted verdigris at bay. A bit of heatshrink tube doesn't go amiss, either.
Getting back to the original thread (sort of), try punching the following digits in your calculator...
0.1267 + 0.6467 =
...then read the result with the calculator held upside-down.
I know, I know. But it *is* Sunday and I'm bored witless.
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and a big HELLO to you too. try 71077345 upside down. i'm bored too, waiting for the MONACO GP to start followed by the INDY 500.
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Perhaps a tad more readable with a decimal point between the "0" and the second "7".
And more...
53045
58008 (you need a bit of imagination with the number 8 on that one).
0.0761
5604
3376
57714
57716
5317.037
...... etc, blah.
Gawd, I'm *still* bored.
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55378008 if you calculator has enough numbers
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55378008 if you calculator has enough numbers
Now your gretting in my area and I forgot, didn't have to turn them upside down here %% %% {-) {-) {-)
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LOL, Changes in Latitudes, Changes in Attitudes!
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PMK,
Why must you start me off thinking? Re your replies 46/49.
Fuses in the +ve side, logical to most people if you consider the definition of a fuse ie to isolate a circuit or device from the source of potential in the event of a fault. In most peoples minds a +ve voltage is a potential while a 0v is not.
I'll refrain from the power field solutions of old (fuses in both poles) and the problems that came from this such as the -ve fuse blowing while the +ve still maintained full voltage on the circuit. Painful - from bitter experience. You may still find examples of this practice in areas that were once supplied from tramways system and later converted to AC. It's nasty but will likely be around until long after I've been "connected to earth".
It links with your discussion of current flow and electron flow. Have you ever used the widely used analogy of water flow in current flow?
People (ie the human mind) can accept the idea of water flowing from a raised bucket (representing a potential) to a bucket at ground level, but try to convince them that really the flow is from the ground up to the bucket and they'll get the sleeveless jacket out for you.
In days of old (before electronics came into the open) it made little difference to anyone. But as a student in the early 60's it screwed our minds up when we started on valve theory.
There's still your theory of the ammeter to be considered.... Those Green Shield stamps look appealing, I'm looking at very obscure ideas for that one.
More when my cell resumes normal life.
Keep the faith Mate, Rock ON.
Regards
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PMK, thats quite an interesting question you have raised on current.
I believe the reason for a more accurate reading at the negative terminal over the positive
terminal would be to do with the fact that electrons move from negative to positive as you
have stated.
Now considering this and disregarding the common convention of current flow the current
measured at the negative terminal is the whole current released from the power source.
When the current is measured at the positive, the electrons have had to pass through the
circuit and the load in that circuit. therefore, the current may be slightly altered due to losses
as the electrons have passed through the load. I am not 100% sure what these losses are
but I would imagine heat would be a contributing factor, after all any resistance will produce
some heat.
Just my 2 cents worth %)
Tim
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PMK, thats quite an interesting question you have raised on current.
I believe the reason for a more accurate reading at the negative terminal over the positive
terminal would be to do with the fact that electrons move from negative to positive as you
have stated.
Now considering this and disregarding the common convention of current flow the current
measured at the negative terminal is the whole current released from the power source.
When the current is measured at the positive, the electrons have had to pass through the
circuit and the load in that circuit. therefore, the current may be slightly altered due to losses
as the electrons have passed through the load. I am not 100% sure what these losses are
but I would imagine heat would be a contributing factor, after all any resistance will produce
some heat.
Just my 2 cents worth %)
Tim
Could be on to something with leakage. Maybe some conversion to heat and electromagnetic waves has an effect on losses.
Dunno
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hi PMK, I think this is my 500th posting, so it is nice to use it to say thanks PMK and to all those others that have been kind enough to respond to my queries.
There is always something new to learn, my problem is that I may have hit full storage and for every new thing learnt something else gets forgotten, but I can't remember what!
regards Roy