Without any stoppage, a person travels a certain distance at an average speed of 42 km/h, and with stoppages he covers the same distance at an average speed of 28 km/h. How many minutes per hour does he stop?

To solve this problem, we first need to understand that the difference in speed is due to the stoppages.

1. The person travels at an average speed of 42 km/h without any stoppages.
2. With stoppages, the average speed decreases to 28 km/h.

The difference in speed is 42 km/h - 28 km/h = 14 km/h. This means that the person spends time equivalent to traveling 14 km at a speed of 42 km/h on stoppages.

To find out how many minutes this is, we need to calculate the time it would take to travel 14 km at a speed of 42 km/h.

The formula to calculate time is distance/speed. So, the time spent on stoppages in hours is 14 km / 42 km/h = 0.333 hours.

To convert this time into minutes, we multiply by 60 (since there are 60 minutes in an hour). So, the time spent on stoppages is 0.333 hours * 60 minutes/hour = 20 minutes.

Therefore, the person stops for 20 minutes every hour.