Multiple choice

A boy travels from A to B at 60 km/hr. On the return journey, he increases his speed by 25%. What is the average speed for the whole journey?

  1. 50.25 km/hr

  2. 66.67 km/hr

  3. 80.67 km/hr

  4. 75.33 km/hr

  5. None of these

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Speed 1 = 60 km/hr. Speed 2 = 60 * 1.25 = 75 km/hr. Average speed = (2 * v1 * v2) / (v1 + v2) = (2 * 60 * 75) / (60 + 75) = 9000 / 135 = 66.67 km/hr.

AI explanation

The return speed is increased by 25 percent, making it 60 multiplied by 1.25, which equals 75 km/hr. Using the average speed formula for equal distances, 2xy divided by (x plus y), we get 2 multiplied by 60 multiplied by 75 divided by the sum of 60 and 75. This calculates to 9000 divided by 135, which equals 66.67 km/hr.