Question 1034969: There are 3 different trains. One train leaves every 15 min, the other leaves every 20min and the last one leaves every 45 min. They all leave at 6:15 what time do they leave again at the same time
Answer by fractalier(6550)   (Show Source):
You can put this solution on YOUR website! This is asking you to find the first common multiple of 15, 20 and 45.
You can do this by listing their multiples or by finding their prime factorizations...without having to show you that second method, let's list 'em:
15,30,45,60,75,90,105,120,135,150,165,180
20,40,60,80,100,120,140,160,180
45,90,135,180
You can see that the first number that is on all three lists is 180 minutes.
So 180 minutes after 6:15 is 9:15.
By the way,
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