How do you find the Lcm of 20,24?

Question

5486 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-11-08T19:47:22

120

one quick way is to use the relation

$GCFxxLCM=axxb$

$GCF(20,24)=4$

$LCMxx4=20xx24$

$LCM=(20xx24)/4$

$LCM=(cancel(20)^5xx24)/cancel(4$

$=120$

Answer 2 · 2016-11-12T22:01:46

A bit of a cheat method.

Lowest common multiple is 120

Any multiple of 20 ends with the digit 0

So all we need to do is determine the first multiple of 4 from 24 that ends with the digit 0.

$1xx4 = 4 color(red)(" "larr "Fail")$
$2xx4=8color(red)(" "larr "Fail")$
$3xx4=12color(red)(" "larr "Fail")$
$4xx4=16color(red)(" "larr "Fail")$

$5xx4=20 color(green)(" "larr "Works")$

Thus we have $" "5xx24= 120$

Lowest common multiple is 120