Make diagrams in races. They help you understand the question better.

Jerry gives Jim a head start of 200 m so Jim starts not from the starting point but from 200 m ahead. Jerry still beats him by 30 sec which means that Jerry completes the race while Jim takes another 30 sec to complete it.
In this race, Jerry covers 2000m. In the same time, Jim covers the distance shown by the red line. Since Jim needs another 30 sec ( i.e. 1/2 min) to cover the distance, he has not covered the green line distance which is (1/2)*s where s is the speed of Jim. The distance Jim has actually covered in the same time as Jerry is [1800 - (1/2)*s] shown by the red line.


Jerry gives Jim a start of 3 mins means Jim starts running first while Jerry sits at the starting point. After 3 mins, Jerry starts running too. Now, Jim beats Jerry by 1000 m which means that Jim reaches the end point while Jerry is still 1000 m away from the end.

In this race, Jerry covers a distance of 1000 m only. In that time, Jim covers the distance shown by the red line (the distance before that was covered by Jim in his first 3 mins). This distance shown by the red line is given by 2000 - 3s (3s is the distance covered by Jim in 3 minutes)

Now you see that in the first race, Jerry covers 2000m while in the second race, he covers only 1000m. So in the second race, he must have run for only half the time. Therefore, in half the time, Jim would also have covered half the previous distance i.e. the second red line will be half the first red line.

First red line = 2*second red line
1800 - (1/2)s = 2*(2000 - 3s) (where s is the speed of Jim in m/min)
s = 400 m/min

Time taken by Jim to run a 2000 m race = 2000/400 = 5 min

Answer (B)
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It's a tough question. DO you have the OA? I'm not sure how to work this one out.
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Thanks so much!! +1

I tried to solve it by writing down the tables for the 2 races and tried to find relationships between the R,T,D, but it took way much time.

I have given more details next to the relevant diagrams in the post above.
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Karishma,

thanks for that wonderful explanation . i was just trying to arrive at the answer in a little diff way .. i.e equating the times
so i get something i like this

1800/s -1/2 =2000/s-3

so im just equating the time taken by Jim across both the races and when i compare it with the equation you have come up with , I realised that i have mafe a mistake and tried to see how it went wrong bu unable to.
Can you please help me with this?

According to this equation, time taken by Jim in the first race is same as the time taken by him in the second race. But that is not true. In the second race, he covers half the distance he covered in the first race (since in the same time, Jerry covered half the distance too. Since their speeds are constant in the 2 races, the time in the second race must be half)
Otherwise your equation is the same as mine

1800/s -1/2 = 2(2000/s-3)
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Wow tough problem, still trying to grasp it.

Explained beautifully . A small typing error.

Hi Bunuel,

Can you add your spin to this question and advise on how to about solving it?

Thanks,
AJ

I don't understand the logic behind this equation: 2,000*(t-30)=1800*t
This implies Jerry's Distance * Jerry's Time = Jim's Distance * Jim's Time
Why?
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