1.

The ratio of average speed of onward to the average speed of return journey is 7 ∶ 5. If the time taken in the whole journey of 490 km is 24 hours. Find the speed of train in onward journey?1. 34.5 km / hr2. 24.5 km / hr3. 12.5 km / hr4. 45.5 km / hr5. 15.5 km / hr

Answer» 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


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