# 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.

Lets time ratio is =
A : B A : B
36:45 => 4:5.

The speed ratio is;
A : B
5 : 4.

If a completes 100 with 5 units of speed, then B completes 80 with 4 units of speed.
(1)

Sheth said:   3 years ago
Time ratio = 36:45 = 4:5.
Speed ratio = 5:4.
when A complete 5 B complete 4.

A complete 100 B complete 100*4/5 = 80m so A beat B by 20m.
(1)

Purushotham Reddy said:   6 years ago
20P---28P------100P.
A---- B ---- C.

Here, the difference between B and c is 8 points when you calculate only for 80 Points (from B to 100).
So 8 Points - 80 Points.
But we need for 100 points.
Then 8p -80p.
10P-100P.

Hope you understand.

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 .
(1)

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.

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

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

100-80 = 20.

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.

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.