Four runners A, B, C and D are running around in a circle, 1680 meter in circumference, at 8 mpm, 12 mpm, 16 mpm and 20 mpm respectively. If they start at the same time from the same point in the same direction, when will they be together again at the starting point for the first time?
Explanation:
A completes one round of the circle in (1680/8) = 210 minutes
B completes one round of the circle in (1680/12) = 140 minutes
C completes one round of the circle in (1680/16) = 105 minutes
D completes one round of the circle in (1680/20) = 84 minutes
They will meet at the starting point for the first time at LCM (210, 140, 105, 84) i.e. 420 minutes or 7 hours.
Hence, option (e).
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