A boat's speed in still water is 15 km/h and the current is 3 km/h. What distance is covered downstream in 12 minutes?

Given data

• Speed in still water, u = 15 km/h
• Speed of current, v = 3 km/h
• Time downstream, t = 12 minutes

Concept / Approach

• Downstream speed = u + v (current aids motion).
• Distance = Speed × Time (time in hours).

Step-by-step calculation

Downstream speed = u + v = 15 + 3 = 18 km/hConvert time: 12 min = 12/60 = 0.2 hDistance = 18 × 0.2 = 3.6 km

Verification

In 1 hour at 18 km/h, distance = 18 km. In 0.2 h, 18 × 0.2 = 3.6 km.

Common pitfalls

• Using u − v instead of u + v for downstream.
• Forgetting to convert minutes to hours.

Final Answer

3.6 km