Concept:The question tests on the application of Rates(Time-Speed-Distance) in a Race question
1st Race
Let Jerry take x sec
=>Jim would take (x+30) sec to complete the same race
 =>Jerry’s speed = Distance of the race/His speed
= 2000 / x m/s
 Jim’s speed= Distance of the race/His speed
=1800 / (x+30) m/s

2nd Race
 Let Jerry take y sec to cover the race.
Jerry has not covered the 2000m; instead he is beaten by 1000m
=>He has covered 2000-1000 = 1000m in y sec
=> Jerry’s speed here = 1000/y m/s

 Jim gets a start of 3min or 180sec
=> He gets 180 sec additionally for the race and he also completes the 2000 m race
  • Speed  of Jim = 2000 / (180+y)m/s  ----------(1)

     
  • That means, 2000/x = 1000/y (Equating Jerry’s speed from both races)
 
=> y=x/2

 => 1800 / (x+30) = 4000 / (360 + y ) (Substitute y=x/2 in eq(1))

 =>2200x = 526000
 
 => x = 239 seconds.

 Hence, Jerry will complete 2000m race in 2000/239
 
= 3.98 ~= 4 minutes.  (You may not need to solve ahead as the option b starts for Jerry with 4)

 Speed of Jim is 1800 / (239+30)
 
= 6.69 m/s
 
=> The time required for Jim to finish 2000m = 2000/6.69 = 298.95 s

Therefore, the time required in minutes = 298.95/60 = 4.98 ~= 5 minutes.(B)