# Aptitude - Races and Games - Discussion

Discussion Forum : Races and Games - General Questions (Q.No. 7)
7.
In 100 m race, A covers the distance in 36 seconds and B in 45 seconds. In this race A beats B by:
20 m
25 m
22.5 m
9 m
Explanation:

 Distance covered by B in 9 sec. = 100 x 9 m = 20 m. 45 A beats B by 20 metres.

Discussion:
13 comments Page 1 of 2.

Why we are taking 45 in the solution?

A beats=36sec
B beats=45sec
so 36----45
then 1 part=45/36=5/4
B covers A in 100m race=(4/5)*100=80m
so A beats B by=(total distance)100-B covers(80)
20m faster than B

Himanshu Singla said:   1 decade ago
Here it is given that A can cover 100m in 36 sec and B in 45 sec. So when A reaches finish point B still has 9 sec left of his time to reach the final point. In this time he can cover the remaining distance by which he has been beaten.

In 45sec B can travel 100m.

In 1sec ------------- 100/45.

In 9 sec ------------ (100/45) *9=20 Answer.

HOPE you UNDERSTAND. Please clarify if am wrong.

In 36 seconds B covers (100/45)*36 = 80 meters.

In 36 seconds A covers 100 meters.

So A beat B by 20 meters.

Mridul Chakraborty said:   1 decade ago
Detailed solution for easier interpretation :

Speed of A = 100 (distance)/36 (Time) = 2.78 m/s.
Speed of B = 100(distance)/45(Time) = 2.22 m/s.

Difference in speed between A & B = 0.56 m/s < i.e. 2.78-2.22 m/s>

Hence in 36 seconds in which A finishes the race, B will cover 2.22*36 = 80 meters.

So A finishes the race 20m ahead of B.

NoName said:   9 years ago
A 1sec - (100/36) m.

B 1sec - (100/45) m.

1sec - A is ahead by (100/36-100/45) = 5/9 m.

So, in 36s A is ahead by (5/9*36) = 20 m.

Santhosh said:   8 years ago
36/45*100 = 80.

100-80 = 20.

Student said:   8 years ago
That's a great help thanks a lot!

Speed of A = 100 (distance) /36 (Time) = 2.78 m/s.
Speed of B = 100 (distance) /45 (Time) = 2.22 m/s.
Difference in speed between A & B = 0.56 m/s < i.e. 2.78-2.22 m/s>.
Hence in 36 seconds in which A finishes the race, B will cover 2.22*36 = 80 meters.

So, A finishes the race 20m ahead of B.

Sana said:   6 years ago
Common time difference between A and B is =(45-36)=9sec.

Now, B travel distance 100m in 45sec.
So
45sec ----------> 100m
9sec ------------> (9/45)*100=20m.

This 20m is actual distance between A and B or A beat by B in 20m .
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