My feed
Premium

Please
or
to access all these features

Connect with other parents whose children are starting secondary school on this forum.

Secondary education

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

17 replies

Spidermama · 26/09/2011 16:19

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?

Thanks.

OP posts:
Report
GlaikitFizzog · 26/09/2011 16:22
Report
Spidermama · 26/09/2011 16:26

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

OP posts:
Report
iklboo · 26/09/2011 16:26

Will one be 12?

Report
iklboo · 26/09/2011 16:27

No, ignore that!

Report
Spidermama · 26/09/2011 16:32

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

OP posts:
Report
ChazsBrilliantAttitude · 26/09/2011 16:33

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 www.gcsemathstutor.com/lcm.php

Report
iklboo · 26/09/2011 16:35

Think 16 & 18 work.......Confused

Report
Ladymuck · 26/09/2011 16:37

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=24*32 (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 (32) and 16(42) 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.

Report
GlaikitFizzog · 26/09/2011 16:43

Ha Spidermama I'm an Aberdonian! Small world!

Still no idea about the answer though! ;o

Report
GlaikitFizzog · 26/09/2011 16:45
Report
Spidermama · 26/09/2011 16:48

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?

OP posts:
Report
Ladymuck · 26/09/2011 16:54

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.

Report
Spidermama · 26/09/2011 17:05
Thanks
OP posts:
Report
GlaikitFizzog · 26/09/2011 17:09

Nae bad quine! :o

Report
Spidermama · 26/09/2011 17:12

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

OP posts:
Report
GlaikitFizzog · 26/09/2011 17:51

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!

Report
Spidermama · 26/09/2011 18:55

Jeez! It's a sare fecht right enough.

OP posts:
Report
Please create an account

To comment on this thread you need to create a Mumsnet account.