Question

One caution sign flashes ever 4 seconds, and another caution sign flashes every 10 seconds. At a certain instant, the 2 signs flash at the same time. How many seconds elapse until the 2 signs next flash at the same time?
A. 6
B. 7
C.14
D. 20
E. 40

Answer 1

LCM(4,10) = 20

Answer 2

noob