Marathon runner covered the whole distance in 4 hours running at a constant speed of 8.1 km per hour. How long would it take him to cover the same distance if he decreased the speed to 7.2 km per hour?

Answer: it will take him 4.5 hours to cover same distance

Step-by-step explanation:

Marathon runner covered the whole distance in 4 hours running at a constant speed of 8.1 km per hour.

Speed = distance / time

Distance = speed*time

Therefore, distance covered by the marathon runner in in 4 hours, running at a speed of 8.1 km per hour is

8.1 * 4 = 32.4 kilometers

if he decreased the speed to 7.2 km per hour, the distance remains 32.4 kilometers. Therefore,

At 7.2 km per hour, the time it would take him to cover the same distance would be

Distance / speed = 32.4/7.2 = 4.5 hours