A man running at the speed of 10 km/hr takes 7 minutes to travel a certain distance . By how much should he increase his speed (in km/hr) to cover the same distance in 5 minutes ?

04

Distance  =  speed  ×  time 

Time taken = 7 minutes = \(\frac{7}{60}\) hr

Speed = 10 km/hr

Distance  =    10 × \(\frac{7}{60}\)

New time = 5 minutes = \(\frac{5}{60}\) hr

New speed  =  \(\frac{distance}{time}\) =   10 × \(\frac{7}{60}\) ×  \(\frac{60}{5}\)

 New speed = 14 km/hr

Increase in speed =  New speed  -  Old speed 

                          =   14  -   10   = 4 km/hr