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Anyone able to solve this exam question?

35 replies

bartonian · 21/12/2017 09:17

Three whole numbers when added together make 20. When multiplied together they make 300. What are the numbers?

OP posts:
OuchBollocks · 21/12/2017 09:46

I can't do this and it is now driving me mad. I have split 300 into its factors of 2 2 3 5 5, but I can't use them to make 3 numbers that add up to 20, even sneaking in a -1 somewhere.

bartonian · 21/12/2017 10:02

Exactly - we have spent hours on it. But would they put a question that doesn’t work on an exam paper? (past paper, so people actually sat it)

OP posts:
MirandaWest · 21/12/2017 10:07

Will have a think.

Could have two negative and one positive number as those would multiply to make a positive number.

autumncolour · 21/12/2017 10:10

Are you allowed to use negative numbers?

newdocket · 21/12/2017 10:13

Is it -10, 0 and 30?

newdocket · 21/12/2017 10:14

no, because it would then be -300. bugger.

MirandaWest · 21/12/2017 10:14

That won't work as they will be 0 multiplied together

newdocket · 21/12/2017 10:15

No, it would be zero. Even more bugger.

MirandaWest · 21/12/2017 10:15

Also not sure whether negative numbers are whole numbers or not.

StormTreader · 21/12/2017 10:15

Surely this must be a misprint somewhere?

Jesamine · 21/12/2017 10:16

What is the past paper?

newdocket · 21/12/2017 10:17

negative numbers are whole numbers, I'm pretty certain

goose1964 · 21/12/2017 10:26

can it include brackets?

XmasInTintagel · 21/12/2017 10:31

Just found a definition that said whole number are only positive, integers include the negative one too, but I don't think its do able with just positive ones?? What age was this for, and if you have the specific paper we can maybe check if it was an actual mistake?

MongerTruffle · 21/12/2017 10:33

@noblegiraffe will hopefully come and help.

Ifailed · 21/12/2017 10:35

is this definitely in base 10?

XmasInTintagel · 21/12/2017 10:37

It'd work if it had to add up to 21, not 20, any chance it was copied wrong at some point OP?

chemenger · 21/12/2017 10:39

I don’t think it can be done. It works with 4 numbers- 10, 5, 3, 2 but I can’t find three that work.

Ifailed · 21/12/2017 10:44

in base 4:
-2, -2, and 30 (12 in base 10) works:
-2 + -2 + 30 = 20 and -2 x -2 x 30 = 300 . In decimal:
-2 + -2 + 12 = 8 and -2 x -2 x 12 = 48

Outedsochanged · 21/12/2017 10:48

I think it will be 2 negative numbers and one positive. So that the 2 negative multiplied together become a positive. Not the answer, but approaching it....
27-4-3=20
27 x -4 x -3= 324

NotDavidTennant · 21/12/2017 10:51

What is the exact question?

capitalL · 21/12/2017 10:54

I like Ifailed's base 4 answer, because there's definitely no way to do it in base 10 (which you can prove by an exhaustive search if you really want to)

MongerTruffle · 21/12/2017 11:17

If you type the exact question into Google you might find the mark scheme if it's from a past paper.

newdocket · 21/12/2017 11:30

This is driving me nuts. I NEED to know the answer!

MaidenMotherCrone · 21/12/2017 12:26

Is this a GCSE past paper?

I think it's a misprint.

DS says it's not doable!

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