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Tricky maths question

NorthEasterner
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Tricky maths question

What is
40 + 40 x 0 + 1 ?
My calculator shows 41
But my brain calculates as 81
As 40 add 40 = 80
80 times 0 is 80
Plus the 1 = 81
how is this not.  This is mind boggling  Crazy
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30 REPLIES
cyrilclark1
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Re: Tricky maths question

Try the following link: www.answers.yahoo.com/question/index?qid=20111111031940AAK5eno

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Moderator
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Re: Tricky maths question

Is seems that the calculator is treating it as 40 + (40 x 0) + 1 = 41
You are thinking ((40 + 40) x 0) + 1 = 1
80 x 0 = 0 (if you have nothing then 80 times nothing is still nothing)
It could, of course, be 40 + 40 x (0 + 1) = 80
Hope that helps.

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Superuser
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Re: Tricky maths question

Well 80 x 0 would be 0 anyway, so that answer would be 1.
The "correct" interpretation is that multiply (and divide) have higher precedence than add (and subtract) so the 40 x 0 is done first, giving 0, then that is added to the first 40 and the 1 to give 41.
A clearer way of expressing this is to use parentheses, so 40 + (40 x 0) +1 = 41
But it has to be understood the parentheses come first.
David
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Re: Tricky maths question

the operands work in the following order
x and / first left to right
+ and - next left to right
40 + (40 x 0) + 1
the x sign is action first
which leaves 40 + 0 + 1  = 41
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NorthEasterner
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Re: Tricky maths question

Theres lots of ways that you can do this sum.
Maths isn't great thing of me  Wink
Thanks for the replies
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Re: Tricky maths question

Look up BEDMAS (or PEDMAS) and all will become clear. It's 41 by the way (not 42  Cheesy )
Quote from: NorthEasterner
Theres lots of ways that you can do this sum.
No, just one correct way.  Cool
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Re: Tricky maths question

Quote from: NorthEasterner
Theres lots of ways that you can do this sum.

Not really, only the way Mav and journeys showed.
Multiplication first, then division then the addition and subtracting (no order for the last two).
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Thunderclap
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Re: Tricky maths question

In a computer sense 40 + 40 x 0 + 1 by precedence resolves to ( 40 + ( 40 x 0  ) ) + 1  = 41
As a rule, where there is no (  ( grouping ) ), do divides first, then multiplies, then subtractions, then additions [ Subtration beats addition because they needed to assert some rule for computer program compilers ]
So 40 + 40 x 0 - 1 would be 40 + (( 40 x 0 ) - 1 )  or 39
Angry Although doing 40 + 40 x 0 / 5 - 1 might just break the universe..
In computing, precedence can be a pain in the A - which is why brackets are essential to stop you from crashing the banking system with an errant divide before multiply by zero error. True.
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Re: Tricky maths question

@Thunderclap - where has the -1 come from then? - That wasn't in NE's OP..
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Re: Tricky maths question

Quote from: NorthEasterner
40 + 40 x 0 + 1 ?
My calculator shows 41

You've got a very good calculator. Most just work (incorrectly) left to right with no regard to operator precedence.
jelv (a.k.a Spoon Whittler)
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NorthEasterner
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Re: Tricky maths question

This could be a question that will come up in my sons GCSE maths exam.
I asked him about this and he says to use the BODMAS
B= Bracklet
O= Other
D= Divide
M= Multiply
A= Add
S= Subtract
or alternatively BIDMAS where the I stands for Indices
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NorthEasterner
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Re: Tricky maths question

The calculator was on my Samsung Galaxy S4.  Well done Korea  Grin
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Re: Tricky maths question

O stands for Orders  (ie Powers and Square Roots, etc.).
jelv (a.k.a Spoon Whittler)
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NorthEasterner
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Re: Tricky maths question

In my sons exercise book i says 'Other'  Has been marked and noted "Excellent work"
It must have changed since we have left school. 
My son has confirmed it is 'other'
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