A boat can row 36 km upstream in 9 hours and the same distance downstream in 3 hours. What is the speed of the boat in still water ?
Answer & explanation
Correct answer: option 2
We know that,
Speed = Distance/Time
We have,
D = 36 km
Time taken upstream = 9 hours
Time taken downstream = 3 hours
Let's denote the boat's speed in still water = B (km/h), and the speed of the current = C (km/h).
When the boat is rowing upstream =
Relative speed = B - C
B - C = \(\frac{36}{9}\)
B - C = 4 ----------- (x)
When the boat is rowing downstream:
B + C = \(\frac{36}{3}\)
B + C = 12 ----------- (y)
Adding Equation x and Equation y, we get:
B - C + B + C = 4 + 12
2B = 16
B = 8