A boat running up stram takes 6 hours to cover a certain distance, while it takes 10 hours to cover the same distance running down stream. what is the ratio between the speed of the boat and the speed of water current respectively?
Choose the correct choice from the following answers.
A) 2 : 3 B) 5 : 6 C) 4 : 1 D) 7 : 1 E) 8 : 1

Rationale: explanation : let speed of boat is x km / h and speed stream is y km / hr 6 ( x + y ) = 10 ( x - y ) 6 x + 6 y = 10 x - 10 y 16 y = 4 x 4 y = x x / y = 4 / 1 4 : 1 answer : option c
Answer: C