In a race of 1 km A beats B by 120m or 12 seconds. Find the time taken by A to run 1 km?

88 sec

Distance = Speed  × Time

A beats B by 120 m in 12 second , that means B covers 120 m in 12 sec . 

Speed of B = \(\frac{120}{12}\) = 10 m/s

Time to cover 1000 m = 100 sec

A beats B by 12 sec means A reach 12 sec early. 

So, time taken by A to cover to cover 1000 m = 100 - 12 = 88 sec .

Time taken by a to complete the race is 88 sec .