A man’s speed with the current is 15 km/h and the current’s speed is 2.5 km/h. What is his speed against the current?

Q: A man’s speed with the current is 15 km/h and the current’s speed is 2.5 km/h. What is his speed against the current?

Concept / Approach With current: vb + vs; Against current: vb − vs. Step-by-step calculation vb + vs = 15, with vs = 2.5Boat speed in still water vb = 15 − 2.5 = 12.5Against current = 12.5 − 2.5 = 10 km/h Final Answer 10 km/h

Difficulty: Easy

9 km/h
10 km/h
12.5 km/h
13 km/h

Correct Answer: 10 km/h

Explanation:

Concept / Approach

With current: v_b + v_s; Against current: v_b − v_s.

Step-by-step calculation
v_b + v_s = 15, with v_s = 2.5Boat speed in still water v_b = 15 − 2.5 = 12.5Against current = 12.5 − 2.5 = 10 km/h

Final Answer
10 km/h

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