shahnandan wrote:

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?

1 minute

5 minutes

12 minutes

20 minutes

24 minutes

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