Multiple choice

Andrew and his best friend Sein attend the music class together at their college. Both of them finish the class at the same time. After the class, Andrew starts moving towards the football ground at a speed of 3 km per hour and Sein starts walking towards her dance class in the opposite direction at a speed of 4 km per hour. How long will it take for the classmates to be 1 km apart?

  1. 7 minutes

  2. 8 minutes

  3. 8.57 minutes

  4. 9 minutes

  5. 9.20 minutes
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Relative speed = 3 + 4 = 7 km/h. Distance = 1 km. Time = Distance / Speed = 1/7 hours = 60/7 minutes = 8.5714 minutes.

AI explanation

Because they move in opposite directions, their relative speed is the sum of their individual speeds, giving 3 km/h plus 4 km/h to equal 7 km/h. Using the formula time equals distance divided by speed, the time to be 1 km apart is 1 divided by 7 hours. To convert this time to minutes, we multiply by 60 to get 8.57 minutes, so the correct answer is 8.57 minutes.

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