Question

A car is moving at a constant speed of 40 km/h along a straight road which heads towards a large vertical wall and makes sharp ${90}^0$ turn by side of the wall. A fly flying at a constant speed of 100 km/h , starts from the wall towards the car at an instant when the car is 20 km away, flies until it reaches the glasspane of the car and returns to the wall at the same speed. It continues to fly between the car and the wall toll the car makes the ${90}^0$ turn. How many trips has it made between the car and the wall?

• A. 50
• B. 100
• C. 150
• D. infinite

Answer 1

The correct option is D infinite

With each trip the distance between car and fly would reduce, and the fly would travel shorter distance each time. With decreased distance, the fly would take lesser time to go to wall and reach car again. By this time, the distance between car and wall further decreases.

As the distance between car and wall would tend to zero, the number of trips that fly makes would tend to infinity.