In a river from a fixed location, two identical boats start moving up-stream…
2020
In a river from a fixed location, two identical boats start moving up-stream and down-stream, respectively. The speed of the water current in the river is 3km/hour. If the speed of each of the boats in still water is 15km/hour, the separation between the boats after 12 minutes will be
- A.
3.6 km
- B.
5.6 km
- C.
6.0 km
- D.
7.2 km
Attempted by 3 students.
Show answer & explanation
Correct answer: C
The speed of each boat in still water is 15 km/hour and the stream speed is 3 km/hour. Upstream speed = 15 - 3 = 12 km/hour. Downstream speed = 15 + 3 = 18 km/hour. Since the boats move in opposite directions from the same point, their separation speed is 12 + 18 = 30 km/hour. Time = 12 minutes = 12/60 = 0.2 hour. Separation = 30 × 0.2 = 6.0 km. Therefore, option 3 is correct.