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Ohh Nooooooo! Lowest Common Multiple question for dd's homework. Please help!

(18 Posts)
Spidermama Mon 26-Sep-11 16:19:01

I have tried googling with no real luck. I'm trying to help dd with her homework on LCMs and HCFs as I gather they are called now.

Her teacher hasn't given her any method of working these out.

We're stuck on ... Write down 2 numbers with an LCM of 144.

If you know the answer, can you please tell me how you got there?


GlaikitFizzog Mon 26-Sep-11 16:22:44

<pops in to thread thinking she could help, runs away screaming as she realises she can't>
Sorry OP!

Spidermama Mon 26-Sep-11 16:26:30

Thanks for that glaikit. Hiv'nae heard the word glaikit since my days in Aberdeen. Made me laugh.

iklboo Mon 26-Sep-11 16:26:55

Will one be 12?

iklboo Mon 26-Sep-11 16:27:50

No, ignore that!

Spidermama Mon 26-Sep-11 16:32:42

Are you all as bad as me? Come on maths types. Throw us a bone here. confused

iklboo I think the answer will be two multiples of 12.

The definition I found was

"The LCM(lowest common multiple) of two or more numbers is the smallest number that each will divide into exactly."

I worked it out by trial and error on the multiples of 12. Its not 12 and 24 BTW.

This might help

iklboo Mon 26-Sep-11 16:35:04

Think 16 & 18 work.......confused

Ladymuck Mon 26-Sep-11 16:37:46

OK, so you're looking for 2 numbers, both of which are factors of 144.
I would approach this by looking at what are the prime factors of 144. So to do this I would first divide 144 by 2 to give 72, then divide by 2 again to give 36, again by 2 to give 18 and once more to give 9. Dividing 9 by 3 leaves 3, so 144=2^4*3^2 (where ^ = to the power of).

So from this I can see what numbers are going to the factors of 144. As 144 is the LCM I am looking for 2 numbers which do not have a smaller common multiple. I guess at this point experience kicks in, because I can see that 9 (3^2) and 16(4^2) are obviously factors. By checking all of the multiples of 16 up to 144 I can see that none are divisible by 9, so 9 and 16 are 2 numbers with 144 as their LCM.

Not the most elegant of solutions, but one which does at least practice HCFs.

GlaikitFizzog Mon 26-Sep-11 16:43:41

Ha Spidermama I'm an Aberdonian! Small world!

Still no idea about the answer though! ;o

GlaikitFizzog Mon 26-Sep-11 16:45:05

<head explodes at LadyMucks post>

Spidermama Mon 26-Sep-11 16:48:02

Ladymuck that's genius! Thank you so much. I can now teach this to dd as I finally understand it. Very much appreciated as we were stuck despite googling. Are you a maths teacher or just good at maths? smile

Ah fit like Glaikit?

Ladymuck Mon 26-Sep-11 16:54:19

Not a maths teacher, no, and I guess later this evening one may be along with the proper way to do it. But have had to go through similar with ds, so it must be rubbing off.

Spidermama Mon 26-Sep-11 17:05:56


GlaikitFizzog Mon 26-Sep-11 17:09:05

Nae bad quine! grin

Spidermama Mon 26-Sep-11 17:12:37

Wish you could pass me a buttery. They don't sell them in Brighton. grin

GlaikitFizzog Mon 26-Sep-11 17:51:57

They don't sell them here either, I'm just outside Edinburgh now! My Mum sends me aid parcels!! I don;t know if its true but I heard The Aberdeen Buttery Company does mail order! Can;t get decent Mealy pudding here either!

Spidermama Mon 26-Sep-11 18:55:20

Jeez! It's a sare fecht right enough.

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