A Bell Rings Every 20 Seconds, Another Bell Rings Every 60 Seconds. At 4:00 P.M., The Two Bells Ring

A bell rings every 20 seconds, another bell rings every 60 seconds. At 4:00 p.m., the two bells ring simultaneously. At what time will the bells ring again at the same time?

 

Answer:

We want the Least Common Multiple of 18 and 60.

Using our least common multiple of 18 and 60 is 180

180/18 = 10 (18 second periods)

180/60 = 3 (60 second periods)

180 seconds = 3 minutes

So the next time the bells ring simultaneously is 5:00 + 3 = 5:03 pm

Hence the next time the bells ring is 5:03 pm

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