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The speed of a boat is 10 km/h in still water. It covers a distance of 90 km in 15 hours going upstream. What is the speed of the stream?

A6 km/h

B3 km/h

C5 km/h

D4 km/h

Answer:

D. 4 km/h

Read Explanation:

Let speed of the stream be x km/h Upstream speed = 90/15 = 6 km/h 6 = (10 - x) ⇒ 6 = (10 - x) ⇒ x = 4 km/h


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