CP #21

A train travels at an average speed of 200 km/hr without any stoppages. However, its average speed decreases to 120 km/hr on account of stoppages. On an average, how many minutes per hour does the train stop?

Options: 12, 18, 20, 24 minutes.


OA: 24 minutes

Solution:

You have to find out how many minuter PER HOUR does the train stop.

So, use T = 1 hour.

In 1 hour, the train travels 200 km.

If the distance travelled reduces to 120 km, how much time does it take the train to travel a distance of 120 km? The remaining time (1 hour - time taken to travel 120 km) will give us the stoppage time (per hour).

S = D / T

200 = 120 / T

T = 3/5 hour = 3/5 * 60 mins = 36 mins

So the train has taken 36 mins to travel 120 km in 1 hour. This means that the train stopped for how many minutes? 60 - 36 = 24 mins of stoppage time per hour.