- A2.5 km/h
- B5 km/h
- C11.5 km/h
- D3 km/h
Step-by-Step Solution
Downstream = 21 ÷ 1.5 = 14 km/h. Upstream = 21 ÷ (7/3) = 9 km/h. River = (14 − 9) ÷ 2 = 2.5 km/h.
Answer: A) 2.5 km/h
Covering 21 km downstream takes a launch 1 h 30 min, and 21 km upstream takes 2 h 20 min. What is the speed of the river?
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