The speed of a boat in still water is 15 km/h, and the speed of the current is 5 km/h . In how much time ( in hours) will the boat travel a distance of 60 km upstream and the same distance downstream ?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 9.
If the speed of the boat is x km/hr, and the speed of the stream is y km/hr then,
Upstream speed = (x - y) km/hr
Downstream speed = (x + y) km/hr
We know that,
Time = Distance/Time
Now, according to the question
According to the question:
D/(x - y) + D/(x + y) = Time
⇒ 60/(15 - 5) + 60/(15 + 5) = Time
⇒ Time = (60/10 + 60/20)
⇒ Time = (6 + 3) hr
⇒ Time = 9 hrs
Thus,
The time taken by the boat is 9 hours.