A person covers a certain distance with certain speed if he increases his speed by 04 km/hr then he reach 10 min early . Find the time taken by man with his initial speed ,  if his initial speed is 36 km/hr .

100 min

Initial speed = 36 km/hr 

And speed increases by 4 km/hr ,

Increased speed = ( 36 + 4 ) km/hr= 40 km/hr

Ratio             initial speed     :      increased speed

                         36              :           40 

speed                 9               :            10 

time                   10              :            9

 ( Distance = Speed × Time , so ratio of speed and time is inverse to each other  ) 

According to question , ( 10 - 9 )R =  1R = 10 min 

Time taken with initial speed = 10 × 10 = 100 min