In a race of 1 km A beats B by 250m or 25 seconds. Find the time taken by A to run 1 km?

75 sec

Distance = Speed  × Time

A beats B by 250 m in 25 second , that means B covers 250 m in 25 sec . 

Speed of B = \(\frac{250}{25}\) = 10 m/s

Time to cover 1000 m = 100 sec

A beats B by 25 sec means A reach 25 sec early. 

So, time taken by A to cover to cover 1000 m = 100 - 25 = 75 sec .

Time taken by a to complete the race is 75 sec .