Question

If the speed of a boat in still water is 20 km/hr and the speed of the current is 5 km/hr, then the time taken by the boat to travel 100 km with the current is :

• A. 2 hours
• B. 3 hours
• C. 4 hours
• D. 7 hours

Answer 1

Answer:

C. 4 hours

Solution:

Given:

Speed of Boat in Still water, B_S = 20 km/hr

Speed of Current, S_s = 5 km/hr

Distance = 100 km

Calculation:

Rate downstream of boat D_s = B_s+S_s = (20 + 5) kmph = 25kmph

Required time $=\frac{100}{25}=4hours$