A boat covers 120 km in six hours in downstream. The respective ratio of speed…
2025
A boat covers 120 km in six hours in downstream. The respective ratio of speed of boat in still water and speed of stream is 3: 1. If speed of stream is increased by 80%, then find in how much time the boat will cover 84 km in upstream?
Answer: B. 14 hours — Downstream speed = 120/6 = 20 km/h. Boat : stream = 3 : 1, so downstream speed = 4 parts and one part = 5; boat speed = 15 and stream speed = 5. After an 80%…
- A.
12 hours
- B.
14 hours
- C.
10 hours
- D.
15 hours
- E.
16 hours
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Correct answer: B
Downstream speed = 120/6 = 20 km/h. Boat : stream = 3 : 1, so downstream speed = 4 parts and one part = 5; boat speed = 15 and stream speed = 5. After an 80% increase, stream speed = 9, so upstream speed = 15 - 9 = 6 km/h. Time for 84 km = 14 hours.