Multiple choice

A boat is moving 2 km against the current of the stream in 1 hour and moves 1 km in the direction of the current in 10 minutes. How long will it take the boat to go 5 km in stationary water?

  1. 1 hr 20 minutes

  2. 1 hr 30 minutes

  3. 1 hr 15 minutes

  4. 30 minutes

  5. None of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let boat speed be b km/hr and stream speed be s km/hr. Against current: b - s = 2 km/hr (2 km in 1 hour). With current: b + s = 6 km/hr (1 km in 10 minutes). Solving: adding equations gives 2b = 8, so b = 4 km/hr. Time for 5 km in still water = 5/4 = 1.25 hours = 1 hr 15 min.