Question

Two trains each travelling at a speed of $20$ kmph approach each other on the same straight track. A bird that can fly at a speed of $40$ kmph flies off from one train when they are $40$ km apart and heads directly for the other train. On reaching the other train it flies directly back to the first train and so forth. Before the trains crash, the total distance travelled by the bird is

• A. $20km$
• B. $40km$
• C. $80km$
• D. $60km$

Answer 1

Answer: (B)

$40km$

The Time taken till crash $=\frac{distance}{speed}=\frac{40km}{40km/h}=1hr$
Speed of Bird = 40 km/hr
Hence distance travelled $=Speed\times time=40km$