How do you find the LCM of 15, 20?

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Answer 1 · 2016-11-28T14:34:41

60

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#