A can finish 3800m race in 3 min . While B can finish the same race in 3 min 10 sec. By what distance A will defeat B in a race of 3800 m.

200 m

According to question , 

A runs a distance of 3800m in 3 minutes and B runs same distance in 3 minutes 10sec  . 

A  beats B by 10 sec 

Distance travelled by B in  3 minutes 10sec  ( = 190 sec ) = 3800m 

Distance travelled by B in 10 sec = \(\frac{3800\;×\;10}{190}\) = 200m