A,B and C run around a Circular track starting from the

Solution

8km = 8000 m A makes it around the track 10 times (8000/800) in an hour Similarly B = 15 times and C = 20 times in an hour In 60 minutes, A will complete track once every 6 minutes, B once every 4 minutes and C once every 3 minutes LCM of A,B,C = LCM(6,4 & 3)= 12  Alternative:  Time = Distance/Speed Time for A = 0.8/8 hours Time for B = 0.8/12 hours Time for C = 0.8/16 hours LCM of A,B,C = (LCM of numerator)/(HCF of Denominator) = (LCM of 0.8,0.8,0.8)/(HCF of 8,12,16) = 0.8/4 hours 0.8/4 hours = 12 minutes