OMG! Can't do DD's homework, please help me!

[memoo]

She has asked for my help because she can't do the sum and neither can I!!!!

It says list 3 primary numbers that when multiplied add up to 231!!

3 7 and 11 - if it ends in 1 it is likely to be divisble 11 or 7

oh god I so don't get maths!

Thanks Liz

By 'primary number' I'm assuming it means prime number which is a number that can only be divided by itself or 1 e.g. 1, 3, 5, 7, 9...

Your DD is probably expected to try a trial and error approach to this using her knowledge of prime numbers and possibly inverse operations so, if I was her teacher I'd expect to see workings that show she's divided 231 by 9, then 7, then 3 or whatever and then attempted 9, then 5, then 3 and so on until she's come up with the answer OR would hope she'd tried a systematic approach of multiplying three of them together until she gets closer and changing the numbers 'intelligently' if she realises she's way out e.g. 1x3x5=15 so I'd expect the next trial to use much bigger numbers e.g. 5x7x9=315 Her third attempt should reflect her understanding that as the target number is 231 it lies between her two answers so she needs something inbetween to reach it.

In the KS2 NC tests (aka SATs) pupils are given a mark for using a correct method if they make at least 3 attempts and the attempts straddle the answer or get progressively closer to it.

2 is also a prime number

Sorry NATW... I wasn't trying to imply that 2 isn't a prime number! I was hoping my use of the e.g. and the dots would convey that there were others I'd not included.

Whoops! I suppose that wasn't overly helpful on a post where the OP was requesting useful help .

And 1 bizarrely isn't a prime #

Whoops again.... I've been on maternity leave too long.

Thank you clever ladies!!!

I feel your pain. Give me spellings, verbs, punctuation, any kind of literacy, but not maths!

How old is your dd?

SE13mummy 9 isn't a prime number it can be divided by 3 9 and 1

BBK, I promise I know that really! I desperately need to go back to work so my brain gets used once again.

Just teasing!