CAT/1996

Question . 129

Persons X, Y and Z wish to go from place A to place B, which are separated by a distance of 70 km. All the three persons start off together from A, with X and Y going by Luna at a speed of 20 kmph. X drops Y somewhere along the way and returns to pick up Z, who has already started walking towards B at a speed of 5 kmph. Y, after being dropped by X, starts walking towards B at a speed of 5 kmph. In this manner, all three of them reach B at the same time.

How long does it take them to go from A to B?