A boat running upstream takes 10 hours to cover a certain distance, while it takes 7 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and that of the water current, respectively?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 17 : 3.
Let the speed of boat in still water and speed of current be x and y respectively.
So, speed of boat downstream = x + y
And speed of boat upstream = x - y
Given, distance covered by boat in both the directions is same.
According to the given question,
(x + y) × 7 = (x - y) × 10
⇒ 7x + 7y = 10x - 10y
⇒ 3x = 17y
⇒ x : y = 17 : 3
Hence, the ratio between the speed of the boat and that of the water current is 17 : 3.