A boat travels 40 km upstream and then returns downstream to the starting…
2024
A boat travels 40 km upstream and then returns downstream to the starting point in a river flowing at 2 km/hr . If the speed of the boat in still water is 6 km/hr . Find the total journey time .
- A.
9 hrs
- B.
10 hrs
- C.
15 hrs
- D.
12 hrs
Attempted by 3 students.
Show answer & explanation
Correct answer: C
Answer: 15 hrs
Key formula: time = distance ÷ speed
Given: speed of boat in still water = 6 km/hr; speed of stream = 2 km/hr.
Upstream speed = 6 − 2 = 4 km/hr.
Downstream speed = 6 + 2 = 8 km/hr.
Time upstream = 40 ÷ 4 = 10 hr.
Time downstream = 40 ÷ 8 = 5 hr.
Total journey time = 10 + 5 = 15 hr.