A, B and C run around a circular track starting from the same point simultaneously and in the same direction at speeds of 4 kmph, 6 kmph and 8 kmph respectively. If the length of the track is 400 meters, when will A, B and C meet at the starting point for the first time after they started the race?
Since we need the starting point, we need to figure out how often they get to the starting point:
A = 4 km/h / 400 m = 10 times/h = every 6 minutes
B = 6 km/h / 400 m = 15 times/h = every 4 minutes
C = 8 km/h / 400 m = 20 times/h = every 3 minutes
We need to find the GCD, which is 2^2*3 = 12, so the cars will meet after 12 minutes at the starting point of the track.
Answer is C