Question

A,B and C start together from the same point to travel around a circular island 30 km in circumference. A and B are travelling in the same direction and C is in the opposite direction. if A travels 5km, B travels 7km and C travels 8km in an hour , they all come together again after​

Answer 1

Sol: Relative speed of A and B = 7 - 5 = 2 km/hr Relative speed of B and C = 8 + 7 = 15 km/hr Time taken for A and B to meet = Distance / Relative speed                                              = 30 / 2                                              = 15 hrs Time taken for B and C to meet = Distance / Relative speed                                               = 30 / 15                                               = 2 hrsTime taken for A, B and C to meet = LCM of 15 hrs and 2 hrs. LCM of 15 and 2 = 15 x 2 = 30 Therefore, A, B and C come together again after 30 hrs.