Aptitude - Races and Games - Discussion
Discussion Forum : Races and Games - General Questions (Q.No. 2)
2.
A and B take part in 100 m race. A runs at 5 kmph. A gives B a start of 8 m and still beats him by 8 seconds. The speed of B is:
Answer: Option
Explanation:
| A's speed = |  |
5 x | 5 |  m/sec |
= | 25 | m/sec. |
| 18 | 18 |
| Time taken by A to cover 100 m = | |
100 x | 18 | sec |
= 72 sec. |
| 25 |
Time taken by B to cover 92 m = (72 + 8) = 80 sec.
| B's speed = |
|
92 | x | 18 | kmph |
= 4.14 kmph. |
| 80 | 5 |
Discussion:
29 comments Page 3 of 3.
Sayed said:
1 decade ago
How A's speed is found ?
Sravs said:
9 years ago
18/5 is the conversion of m/s to km/hr. Because option is in km/hr. We need to convert.
Manisha said:
9 years ago
I can't understand why we have to use 18/5, where it come from? Can anyone explain?
Vinay said:
10 years ago
We have given speed of A = 5 km/h => 5x5/18 = (25/18) speed;
A takes time = 100x (18/25), Time = Distance/Speed;
=72 sec;
Since A beat B by 8 sec.
So total time taken by B = 72+8 = 80 (time);
Since A gives 8 m to B.
So total distance cover by B = 100-8 = 92 (dist);
We know that Speed = Distance/Time;
Now speed of B = 92/80 m/s;
Now converting it into km/h => (92/80) x (18/5).
=> 4.4 answer.
A takes time = 100x (18/25), Time = Distance/Speed;
=72 sec;
Since A beat B by 8 sec.
So total time taken by B = 72+8 = 80 (time);
Since A gives 8 m to B.
So total distance cover by B = 100-8 = 92 (dist);
We know that Speed = Distance/Time;
Now speed of B = 92/80 m/s;
Now converting it into km/h => (92/80) x (18/5).
=> 4.4 answer.
Deepali said:
1 decade ago
How get 18?
Anamika Sinha said:
1 decade ago
How did you get A's speed ? I dint understand. Please explain.
Naresh.Ravula said:
1 decade ago
While finding the speed of the B, why we are using the 92m only instead of 100m?
Jaanvi said:
1 decade ago
@anamika & sayed
A's speed is in kmph. to make it in m/s, 5 is multiplied with 1000/(60X60).
Hence, 5X5/18=25/18
A's speed is in kmph. to make it in m/s, 5 is multiplied with 1000/(60X60).
Hence, 5X5/18=25/18
Sag said:
1 decade ago
We are adding 8 second to cmplete 100m for b. So why his speed is calulated for 92 m. It should be for 100m and answer should be 4. 25.
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