Correct Answer - Option 2 : 24.5 km / hr
Given∶
The ratio of average speed of onward to the the average speed of return journey is 7 ∶ 5.
The time taken in the whole journey of 490 km is 24 hours.
Formula used∶
Average speed = 2 x × y / (x + y)
Calculations∶
Let the average speed of the onward journey be x
Let the average speed of the return journey be y
Average speed = 2 x × y / (x + y)
According to the question∶
average speed of the onward journey 7x
average speed of the return journey 5x
Average speed = (2 × 7x × 5x) / (7x + 5x) = 490 / 24
⇒ x = 3.5
The average speed of the onward journey, 7x = 7 × 3.5
⇒ 24.5 km / hr
