Multiple choice

A carriage driving in a fog passed a man who was walking at a speed of 3 km/h in the same direction. He could see the carriage for 4 minutes and it was visible to him up to a distance of 100 m. What was the speed of the carriage?

  1. 5 1 2 km/h

  2. 1.8 km/h

  3. 4 1 2 km/h

  4. 2 km/h

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The carriage covers 100 m relative to the man in 4 minutes, so its relative speed is 1.5 km/h. Adding the man's 3 km/h speed gives the carriage speed as 4.5 km/h.

AI explanation

The relative speed of the carriage with respect to the man is the distance it travels to pass him divided by the time, so convert 100 meters to 0.1 kilometers and 4 minutes to one fifteenth of an hour. Dividing 0.1 kilometers by one fifteenth of an hour gives a relative speed of 1.5 kilometers per hour. Adding this relative speed to the man's walking speed of 3 kilometers per hour gives the actual carriage speed of 4.5 kilometers per hour.

Keep practicing — related questions