Question

Five children start crying together and cry at intervals of 5, 10, 20, 30 and 40 seconds respectively. How many times will they cry together in 60 minutes

Answer 1

LCM of 5, 10, 20, 30 , 40 second is 120 second.

So they will cry together at the intervals of 120 seconds

As 60 minutes = 60*60 = 3600 seconds

so, no. of times they will cry together = 3600/120

= 30 times