A person covers a certain distance with certain speed if he increases his speed by 04 km/hr then he reach 6 min early . Find the time taken by man with his initial speed ,  if his initial speed is 40 km/hr .

66 min

Initial speed = 40 km/hr 

And speed increases by 4 km/hr ,

Increased speed = ( 40 + 4 ) km/hr= 44 km/hr

Ratio             initial speed     :      increased speed

                         40             :           44 

speed                 10             :            11 

time                   11             :            10

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

According to question , ( 11 - 10 )R =  1R = 6 min 

Time taken with initial speed = 11 × 6 = 66 min