Two racers run at a speed of 100 m/min and 120 m/min, respectively. If the second racer takes 10 minutes less than the first to complete the run, then how long is the race?

6 km

As we know,

Time is inversely proportional to speed.

 Ratio of two racers ,     

Speed                       100   :    120

                                    5   :   6

                                    6   :   5


According to question   ,

6R - 5R = 1R

 1R = 10 min

Time taken by first racer to complete race = 6 × 10 = 60 min

Distance = Speed × Time
So ,  Distance = 60 × 100 = 6000 m = 6 km