# Talk

## Maths homework showing working out

(21 Posts)
Emochild Mon 17-Oct-16 21:54:18

xxx = 3024

9x8x7x6=3024

But how the heck does dd show her working?

I thought it was a trial and error question but apparently not and her teacher has told her off previously for not showing working

-all numbers have to be less than 10

PberryT Mon 17-Oct-16 21:58:36

Can she break down 3024 into prime factors using the tree?

3024= 3x3x2x2x2x2x3x7 and then the prime factors multiply to get the numbers in the sum. Eg 9 is 3x3

Mon 17-Oct-16 21:59:41

Does the xxx stand for the digits?
She can find the prime factors first of 3024 using something like a prime factor tree then arrange as needed.

Emochild Mon 17-Oct-16 22:00:03

Sorry, that didn't display properly

?x?x?x?=3024

Mon 17-Oct-16 22:05:13

ok, once you have the prime factors then you just have to group them into 4 groups so that each multiple is 9 or less.

Emochild Mon 17-Oct-16 22:28:23

So a cherry tree thingy?

Emochild Mon 17-Oct-16 22:28:41

I'm so technical

Mon 17-Oct-16 22:37:27

in the morning, if no one else has done it I'll sketch it out and take a photo.

Emochild Tue 18-Oct-16 00:11:04

Thank you

The way dd worked it out was...

'I know 3000 and 24 are both in the 6 times table so that's my first number
3024/6=504
I know 504 is in the 4 times table and the 8 times table
504/8=63
7x9=63

So the numbers must be 6x8x7x9'

Works but long winded and not mathematical enough apparently

Tue 18-Oct-16 08:45:19

Odd, I'd consider that mathematical enough - though she could have started with I know that 3024 is divisible by 6 because it is an even number and the digits add to a multiple of 3.

Tue 18-Oct-16 08:51:56

here is how I'd do it.

Emochild Tue 18-Oct-16 18:59:48

Thank you

No doubt I shall be back next week for more help

Tue 18-Oct-16 19:04:10

MooPointCowsOpinion Tue 18-Oct-16 19:07:41

Her working out is fine to show how she did it, I'd be happy with that.

What did she do wrong before?

The only thing I can think perhaps she was specifically told to relate it to the topic of prime factor decomposition.

Emochild Tue 18-Oct-16 19:13:01

Nope

No instructions other than what are the numbers

The same homework included compound interest and fractions with negative exponents

So a fun time was had all round!

Emochild Tue 18-Oct-16 19:14:33

She was previously told off for not showing her working when the question was

3 to the power of 25= ?

3x3x3x3x3...............

MooPointCowsOpinion Tue 18-Oct-16 19:39:03

25 3s! Screw that for a laugh!

Mine might write 3 x 3 x 3 ..... X 3 with a small indication that the ... Means a total of 25 times.

That teacher really likes people showing their working.

Emochild Tue 18-Oct-16 21:13:43

Which is ironic because she gives questions like....

Give the value of (8/27)^-2/3

With no worked examples in their book or a text book to refer to!

cdtaylornats Tue 18-Oct-16 21:34:46

3+0+2+4 = 9 so 3024 is divisible by 9

3^25 = 3^5*3^5*3^5*3^5*3^5 = 243^5 = 847288609443

MooPointCowsOpinion Wed 19-Oct-16 19:11:13

Emochild that's a grade A indices question.

Has to be done in 3 parts, I'd do ^1/3 first (cube root) then ^2 then ^-1 (flips the fraction) to get 9/4.

Emochild Wed 19-Oct-16 22:51:55

Thanks moo and OYBK

I'm guessing you are both maths teachers?

I'm toying with speaking to the school about it but they've recently removed the ability to contact specific departments -you have to email the info@school email and hope it gets through to the right person

Also don't want to piss the teacher off so she takes it out on dd

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