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
2 answers
LCM(4,10) = 20
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