A boats man can row in still water at speed of 7 km/hr. It takes 6 hours more to travel the same distance in upstream than in downstream if the speed of the river is 3 km/hr. what is the distance between the two destinations?	Choose the correct choice from the following answers.
A) 40  B) 87  C) 126  D) 18  E) 91

Rationale: explanation : x = 7 km / hr ; y = 3 km / hr ds = 10 km / hr ; us = 4 km / hr distance ( d ) is same . therefore , if time taken for downstream is t hours , the time for upstream is ( t + 6 ) hours . 10 * t = 4 * ( t + 6 ) 6 t = 24 ; t = 4 hours d = 10 * 4 = 40 km answer : a
Answer: A