## Tricky maths question

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##### Tricky maths question

##### Tricky maths question

16-11-2013 7:20 PM

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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

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 7:34 PM

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My brain hurts - I shall now have to go and lie down!

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 7:37 PM

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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.

**Forum Moderator** and ** Customer***Courage is resistance to fear, mastery of fear, not absence of fear - Mark Twain*

He who feared he would not succeed sat still

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 7:39 PM

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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.

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 7:40 PM

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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

Mav got in before me

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 7:45 PM

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Maths isn't great thing of me

Thanks for the replies

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 7:51 PM

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No, just one correct way.

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

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 8:11 PM

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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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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 8:53 PM

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*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

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

##### Re: Tricky maths question

16-11-2013 8:56 PM

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 9:06 PM

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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) Why I have left Plusnet (warning: long post!) Broadband: Andrews & Arnold Home::1 (FTTC 80/20) Line rental: Pulse 8 Home Line Rental (£13/month) Mobile: iD mobile (£4/month) |

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 9:07 PM

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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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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 9:07 PM

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 9:13 PM

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jelv (a.k.a Spoon Whittler) Why I have left Plusnet (warning: long post!) Broadband: Andrews & Arnold Home::1 (FTTC 80/20) Line rental: Pulse 8 Home Line Rental (£13/month) Mobile: iD mobile (£4/month) |

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##### Re: Tricky maths question

##### Re: Tricky maths question

16-11-2013 9:17 PM

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It must have changed since we have left school.

My son has confirmed it is 'other'

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