Question

A beacon flashes a light regularly 5 times a minute. A neighboring beacon flashes a light regularly 4 times a minute.

If they shine their lights at the same time, after how many ,begin emphasis,seconds,end emphasis, will they flash at the same time again?

Answer 1

they will flash together every 20 seconds. 

Answer 2

This question requires you to find the lowest number in common to both of these sequences. You can find this by multiplying four and five, which gives twenty seconds as the point there these sequences will converge.