<PRE><B>Question 38884</B>
LCM .... the number they all go into.
12 : 12 24 36 48 60 72 84 96 108 120
20 : 20 40 60 80 100 120
35 : 35 70 105 140

Continue listing numbers in this fashion until you find the one that is shared for all three.

Another approach is to multiply them.
12 * 20 = 240 .... 35 does not go into 240
12 * 35 = 420 .... 20 DOES go into 420 
420 is your LCM
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