Question

A hot air balloon is fitted with an engine that can move the balloon at a speed of 20 km/h in still air. There is air blowing from east to west at a speed of 10 km/h and the balloon is moving towards east. It reached the destination in 5 hours. Find the time it would take to return to its original position given that all other conditions remain the same.

• A. 3 hours 15 minutes
• B. 2 hours 08 minutes
• C. 1 hour 40 minutes
• D. None of the above

Answer 1

The correct option is C 1 hour 40 minutes

As the balloon is moving against the air, its effective speed will be (20 – 10) km/h = 10 km/h

It took 5 hours to reach the destination. Hence, the distance is 10 × 5 = 50 km.

While returning, the balloon is moving along the air.

Hence, the speed will be (20 + 10) km/h = 30 km/h

Time taken = 50/30 hours = 5/3 hours = 1 hour 40 minutes