Multiple choice

A rail engine is moving at a uniform speed of 30 km per hour towards a place A. When the engine is still 20 km away from A, an insect starts at A and shuttles between A and engine at a uniform speed of 42 km per hour. The total distance travelled by the insect, by the time engine reaches A is, in km.

  1. 28

  2. 30

  3. 20

  4. 42
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A Correct answer
Explanation

Time for engine to reach A = 20 km / 30 km/h = 2/3 hours. Insect speed = 42 km/h. Distance = Speed * Time = 42 * (2/3) = 28 km.

AI explanation

The insect travels until the engine reaches place A, so we first calculate the time taken by the engine. Using the time formula, time equals distance divided by speed, the engine takes 20 km divided by 30 km/hr, which equals 2 divided by 3 hours. During this entire time, the insect travels at its constant speed of 42 km/hr. Using the distance formula, distance equals speed multiplied by time, the total distance covered by the insect is 42 multiplied by (2 divided by 3), which gives 28 km.

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