Question

How do you find the LCM of 15, 20?

Answer 1

60

Explanation:

method 1

write out the multiples of both numbers until the lowest common one id found

multiples 15:`" "{15,30, 45,color(blue)60,75,90,105,color(blue)120,135,...}`

multiples 20:`" "{20,40,color(blue)60, 80,100,color(blue)120,...}`

`LCM(15,20)=60`

method 2

use `hcfxxlcm=axxb`

`hcf=gcm(15,20)=5`

so`" "5xxlcm=15xx20`

`lcm=(15xx20)/5`

cancel before evaluating makes it easier.

`lcm=(cancel(15)^3xx20)/cancel(5)=60`