Multiple choice

Two trains, each having a speed of $30 {km}/{h}$, are headed at each other on the same track. A bird flies off one train to another with a constant speed of $60 {km}/{h}$ when they are $60 km$ apart till before they crash. Find the distance covered by the bird and how many trips the bird can make from one train to other before they crash?

  1. $70 km$, infinity
  2. $60 km$, infinity
  3. $80 km$, infinity
  4. $90 km$, infinity
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Time until crash = Distance / Relative Speed = 60 / (30+30) = 1 hour. Bird speed = 60 km/h. Distance covered by bird = 60 km/h * 1 hour = 60 km. The number of trips is infinite because the bird's speed is constant and the distance between trains decreases continuously.

AI explanation

The relative speed of the two trains moving towards each other is 30 km/h plus 30 km/h, totaling 60 km/h. The time until the trains crash is the initial distance of 60 km divided by their relative speed of 60 km/h, resulting in exactly 1 hour. The bird flies continuously at 60 km/h for this entire 1 hour, meaning the distance covered by the bird is 60 km multiplied by 1, which is 60 km. Since the distance halves with each trip, the bird makes an infinite number of trips before the crash.

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