A boy goes from home to school at a speed of 30 km/h and returns back at a speed of 70 km/h. What is his average speed for the journey?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 42 km/h.
A boy goes from home to school at a speed of 30 km/h
He returns at a speed of 70 km/h
Average speed = 2xy/(x + y)
where x is speed during home to school
y is the speed of school to home
Average speed = 2 × 30 × 70/(70 + 30) = 4200/100 = 42 km/h