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Poll - What is 3+4x5?
flibble - 20/8/12 at 01:40 PM

Just in the middle of a minor disagreement and wondering if I'm in the wrong (I won't say which I think it is)

Irony - 20/8/12 at 01:50 PM

23. Multiplication comes before addition. The expression would be written 5(3+4) = 35


Wow - my A-level in maths has just proved useful!

[Edited on 20/8/12 by Irony]

blakep82 - 20/8/12 at 01:52 PM

if its as is there, then if you put it in a calculator, its 35.
if any parts are in brackets, ie 3+(4x5) then its 23, as its 3+ the answer of 4x5.

Rod Ends - 20/8/12 at 01:54 PM

BODMAS - O level Maths - (which doesn't exist anymore) - it's called A level Maths!

loggyboy - 20/8/12 at 01:57 PM

Surely if you multiply first the answer is 23:

3+(4*5) :-
3+20=23

blakep82 - 20/8/12 at 02:01 PM

http://www.wolframalpha.com/input/?i=3%2B4x5

hmm, can't argue with that, but i don't really understand it lol

Dale - 20/8/12 at 02:02 PM

Loggyboy is correct as I remember. enter it into google and it also shows 23
Brakets are assumed around the mulitiplication.
Dale

MikeRJ - 20/8/12 at 02:06 PM

quote:
Originally posted by Irony
Multiplication comes before addition. The expression would be written 5(3+4) = 35

Wow - my A-level in maths has just proved useful!


Except that you've just forced the addition to be completed before the multiplication by adding parentheses, and therefore get the wrong answer!

If you are using the standard rules of operator precedence then:

3+4x5 = 3+(4x5) = 23

quote:
Originally posted by blakep82
if its as is there, then if you put it in a calculator, its 35.


Only if your calculator is broken!

[Edited on 20/8/12 by MikeRJ]

bartonp - 20/8/12 at 02:07 PM

Let me correct the sum for you:

4 5 x 3 + =23

(RPN)

stevegough - 20/8/12 at 02:10 PM

Aye. BODMAS. Remember it well.

Brackets,
Order,
Division,
Multiplication,
Addition,
Subtraction.

As there are no brackets, you follow the order.

Hence 3+4 = 7, then 7x5 = 35.

God, is there nothing this forum can't answer?

flibble - 20/8/12 at 02:10 PM

That's quite a split vote so far!
I was taught BIDMAS, yet was having a discussion with my friends daughters teacher who said the above sum gives 35, I said 23 and wondered if things had changed or if I'm having a dopey moment (which is quite possible)!

As a side note to education, I've always kept my books etc from the start of school, and if I look back through them it seems what I learnt aged 6, they're teaching similar at aged 8+.
By age 5 I could count and write (as could all my friends) to a fair degree but none of my friends children could until much later and still seemed to be praised as high achievers at school.

Edit, we were told to swap the Order for Indeces to clear things up?

[Edited on 20-8-12 by flibble]

Confused but excited. - 20/8/12 at 02:15 PM

quote:
Originally posted by stevegough
Aye. BODMAS. Remember it well.

Brackets,
Order,
Division,
Multiplication,
Addition,
Subtraction.

As there are no brackets, you follow the order.

Hence 3+4 = 7, then 7x5 = 35.

God, is there nothing this forum can't answer?


If you actually follow your own reasoning, ie; BODMAS, and follow the order, then multiplication still comes before addition and the correct answer is still 23!

blakep82 - 20/8/12 at 02:15 PM

^ so since the 3 is before the 4, is it then 5x3 (=15) +4 which is 19 lol

quote:
Originally posted by MikeRJ

quote:
Originally posted by blakep82
if its as is there, then if you put it in a calculator, its 35.


Only if your calculator is broken!

[Edited on 20/8/12 by MikeRJ]


well, depends how the calculator works its seems. windows calculator comes up with 35 when you type 3+4x5 and then =
my phone comes up with 19 when you type in 3+4x5 and then =

the calulator on windows works out the sum when ever you type in an action (+, -, x etc) my phone doesn't, it only works out an answer when you press =

i was terrible at maths in school, but i don't remember any mention of multiplications being done before anything else, only ever things in brackets should be done before anything before or after. weird how a simple sum can get different wrong answers

[Edited on 20/8/12 by blakep82]

whitestu - 20/8/12 at 02:19 PM

quote:

If you actually follow your own reasoning, ie; BODMAS, and follow the order, then multiplication still comes before addition and the correct answer is still 23!


Just what I was thinking! The answer is 23. I've checked this with my 10yr old so I'm sure it is correct, as he has had this stuff drilled into him for the last year in preparation for his 11+!

loggyboy - 20/8/12 at 02:20 PM

quote:
Originally posted by stevegough
Aye. BODMAS. Remember it well.

Brackets,
Order,
Division,
Multiplication,
Addition,
Subtraction.

As there are no brackets, you follow the order.

Hence 3+4 = 7, then 7x5 = 35.

God, is there nothing this forum can't answer?


LOL obviously not that well!
The O stands for powers Of (not order!)

Those refering to calculators, i seem to recal their being types that worked out using bodmas, and cheaper ones that didnt. So its all down to user inputing it correctly.
Either way the correct answer is 23

[Edited on 20-8-12 by loggyboy]

02GF74 - 20/8/12 at 02:22 PM

there is only one correct answer.

getting different anwers using a phone, calculator, calc.exe, slide rule abacus etc is not the instrument's fault but indicates a lack of understanding by the person using it: garbage in = garbage out.

mutliplication before addition. you cannot argue with maths.

flibble - 20/8/12 at 02:23 PM

quote:

The O stands for powers Of (not order!)


Hence why we were taught to swap the O(rder) for I(ndices), giving BIDMAS

[Edited on 20-8-12 by flibble]

HowardB - 20/8/12 at 02:25 PM

the O in order is not the order in which the calculation is written, but refers to raising a number to an order,.. ie squared or cubed.

BODMAS is the answer, and a proper calculator will always do the sum in that sequence.

the answer is 23

3+4x5=23=3+(4x5)

3+4x4=3+4squared=3+(4x4)=19

hope that helps

mcerd1 - 20/8/12 at 02:27 PM

another vote for BODMAS = 23

that's second year maths for me (the year before standard grades so ~1994 ) - what's an O level ?

quote:
Originally posted by blakep82
if its as is there, then if you put it in a calculator, its 35.

you need a better calculator then

a bog standard calculator expects you to know your BODMAS and adjust your inputs to suit
a better scientific or graphic calculator (or even MS Excel) will give you 23 even without brackets (the type where you type in the whole expression then hit = )

my old casio's all do it correctly (fx-85, 83 etc...) at least the better do it right, there are a few hundred structures around the country that rely on it.......



[Edited on 20/8/2012 by mcerd1]

maccmike - 20/8/12 at 02:28 PM

ill go with 23

02GF74 - 20/8/12 at 02:37 PM

quote:
Originally posted by HowardB

3+4x4=3+4squared=3+(4x4)=19

hope that helps


eh? - how did 3+4x5 become 3x4x4?

your calculator need anew battery.

HowardB - 20/8/12 at 02:41 PM

quote:
Originally posted by 02GF74
quote:
Originally posted by HowardB

3+4x4=3+4squared=3+(4x4)=19

hope that helps


eh? - how did 3+4x5 become 3x4x4?

your calculator need anew battery.


It was an example of how raising a number to a power was the same as multiplication, but different to addition.

Either way the cry of BODMAS is one that needs upheld.

nick205 - 20/8/12 at 03:30 PM

On the calculator side, I notice my phone gives 35 in basic mode and 23 in scientific mode. Windows calculator works the same way too.

britishtrident - 20/8/12 at 03:39 PM

quote:
Originally posted by nick205
On the calculator side, I notice my phone gives 35 in basic mode and 23 in scientific mode. Windows calculator works the same way too.


Thats because in basic mode it is carrying out the operations in the order they are enter which is the only way it can do it.

In scientific mode it treats it was an equation, the operations are carried out after the equation is entered following maths rules it gives multiplication precedence over addition.

myke pocock - 20/8/12 at 04:49 PM

35, the rest of you know NOOOTHING!!!

rachaeljf - 20/8/12 at 04:59 PM

Quoted wrong post!

Anyway, if your calculator gives an answer of 35, get a new calculator!

[Edited on 20/8/12 by rachaeljf]

James - 20/8/12 at 05:07 PM

BODMAS

Not sure about school but I remember my Dad drumming this into me from a young age.

The answer is 23.



Cheers,
James

chillis - 20/8/12 at 06:08 PM

According to my casio fx-85GT Plus its 23,
my Sis who is a maths brainbox says you would never express 3+4x5, it should always have clarification such as brackets so doesn't deserve an answer, 0 out of 10!
If in doubt I would apply bodmas.
According to usborne junior illustrated maths dictionary page 63 'many part calculations' Brackets, Others (such as powers), Division, Multiplication, Addition, Subtraction therfore 4x5=20+3=23, your daughters teacher needs to go back to junior school and learn the stuff they're teaching our 6 yr olds!
What hope do our kidsa have with teachers like that

[Edited on 20/8/12 by chillis]

NeilP - 20/8/12 at 06:18 PM

BODMAS = 23

AndyW - 20/8/12 at 07:04 PM

how about £250 = sports car? now there is another question that no one can answer

spiderman - 20/8/12 at 07:20 PM

quote:
Originally posted by myke pocock
35, the rest of you know NOOOTHING!!!


Troll alert.

SteveWalker - 20/8/12 at 09:04 PM

quote:
Originally posted by blakep82
the calulator on windows works out the sum when ever you type in an action (+, -, x etc) my phone doesn't, it only works out an answer when you press =


The calculator on Windows works as a basic (non-BODMAS) calculator in basic mode and as a proper BODMAS one in scientific mode.

Now how about "3 4 5 * + ." ?

flibble - 20/8/12 at 09:13 PM

quote:

What hope do our kidsa have with teachers like that

About 73.24% hope it seems



[Edited on 20-8-12 by flibble]

craig1410 - 20/8/12 at 10:11 PM

I think this goes to show that not everyone is mathematically (or arithmetically) minded. Nothing wrong with that but definitely worth being more aware of. Just think how many mistakes must happen every day when fundamental arithmetic is so poorly understood by so many.

There is a really good cure for it - try working in a bar without one of those fancy touchscreen tills. I used to work in a pub part-time when at university and you certainly get used to doing arithmetic in your head. I must say though, as a computer programmer, I do sometimes put in parentheses when I know I probably don't need them. Then again when you have multi-variable expressions with a mix of boolean and arithmetic expressions and perhaps a few method calls thrown in, it can get a bit more tricky...

I voted for 23 by the way

Think of it like this: If you are going to buy 5 cocktails and a pint of beer with cocktails at £4 and beer at £3. It would be 5 x £4 = £20 + £3 = £23. You wouldn't expect to have to pay £35 which would be the price of 5 x (Beer + Cocktail) combos. In other words you would want 6 drinks in total not 10 drinks.

I fancy a beer now...

[Edited on 20/8/2012 by craig1410]

TheGiantTribble - 20/8/12 at 10:34 PM

And there was I thinking the answer to everything was 42

mcerd1 - 20/8/12 at 11:22 PM

quote:
Originally posted by craig1410
I must say though, as a computer programmer, I do sometimes put in parentheses when I know I probably don't need them
I was always taught to do the same, it saves alot of questions and mistakes


but 19 votes for 35 is a bit worring

[Edited on 20/8/2012 by mcerd1]

Ninehigh - 20/8/12 at 11:58 PM

quote:
Originally posted by chillis
my Sis who is a maths brainbox says you would never express 3+4x5, it should always have clarification such as brackets so doesn't deserve an answer, 0 out of 10!


There we go, the answer is "That's the wrong type of question"

owelly - 21/8/12 at 02:14 AM

So.....
5+5+5+5x0=...??

Ninehigh - 21/8/12 at 02:29 AM

quote:
Originally posted by owelly
So.....
5+5+5+5x0=...??


Well whichever way you look at that multiplying anything by zero makes zero

Snuggs - 21/8/12 at 05:16 AM

quote:
Originally posted by owelly
So.....
5+5+5+5x0=...??





5+5+5+(5x0)=15

steve m - 21/8/12 at 06:21 AM

Nick Leeson made it 42

scudderfish - 21/8/12 at 08:36 AM

quote:
Originally posted by SteveWalker
Now how about "3 4 5 * + ." ?


ARRRGGGHH! Forth!

Jupiter Ace sucked!

loggyboy - 21/8/12 at 08:41 AM

quote:
Originally posted by Snuggs
quote:
Originally posted by owelly
So.....
5+5+5+5x0=...??


5+5+5+(5x0)=15






Im really looking forward to my little girl growing up and asking me for help with homework, will give me a chance to relearn all the bits I was to undisciplined to pick up when I was younger. The amount of things I look back on now and think - thats obvious, why on earth could I not pick that up when I was 14?!

[Edited on 21-8-12 by loggyboy]

Lightning - 21/8/12 at 09:08 AM

23

chillis - 21/8/12 at 12:20 PM

In an exam you would be expected to apply bodmas unless directed otherwise, such an ambiguous expression would not normally be used except to test students knowledge of bodmas. Applying the rules of bodmas the result is always going to be 23.
If the expression was written (3+4)x5 then it would equal 35
As for 3 4 5 * + that would actually be 345 x + which it not strictly a recognised equasion.

flibble - 21/8/12 at 12:41 PM

quote:

As for 3 4 5 * + that would actually be 345 x + which it not strictly a recognised equasion

^Programming language^, most of which are a bit odd in my limited experience!

chrisxr2 - 21/8/12 at 01:26 PM

23 BODMAS. GCSE Maths 1994