Aptitude - Time and Distance - Discussion
Discussion Forum : Time and Distance - General Questions (Q.No. 12)
12.
Robert is travelling on his cycle and has calculated to reach point A at 2 P.M. if he travels at 10 kmph, he will reach there at 12 noon if he travels at 15 kmph. At what speed must he travel to reach A at 1 P.M.?
Answer: Option
Explanation:
Let the distance travelled by x km.
| Then, | x | - | x | = 2 |
| 10 | 15 |
3x - 2x = 60
x = 60 km.
| Time taken to travel 60 km at 10 km/hr = |  |
60 |  hrs |
= 6 hrs. |
| 10 |
So, Robert started 6 hours before 2 P.M. i.e., at 8 A.M.
 Required speed = |
|
60 | kmph. |
= 12 kmph. |
| 5 |
Discussion:
93 comments Page 5 of 10.
Prawesh Pradhan said:
8 years ago
After finding out the distance.
60/10 - 60/x = 1,
5/x = 1,
x = 5.
60/10 - 60/x = 1,
5/x = 1,
x = 5.
Neha said:
9 years ago
We can solve this problem by using avg.speed 2xy/x+y.
2 * (10 + 15)/10 + 15,
=12 km/h.
2 * (10 + 15)/10 + 15,
=12 km/h.
Ashish said:
9 years ago
Let the distance be covered 'd'.
Case I: d/t = 10.
Case II: d/t - 2 = 15.
Solving both equations we have t = 10 and d = 60.
To find d/(t-1) = ?
Replacing values of 'd' and 't' will give speed as 12 kmph.
Case I: d/t = 10.
Case II: d/t - 2 = 15.
Solving both equations we have t = 10 and d = 60.
To find d/(t-1) = ?
Replacing values of 'd' and 't' will give speed as 12 kmph.
Shahul said:
9 years ago
1st case-.
Speed = 10.
Time = t.
Distance = 10 * t -----> (1).
2nd case.
Speed = 15.
Time = t - 2 (he reach at 2pm at t time so take t-2 for 12pm).
D = 15 * (t - 2) -----> (2).
From 1 and 2.
10 * t = 15 * (t - 2).
15t - 10t = 30.
t = 6.
So he need 5hrs to reach at 1pm (take 6hrs to reach 2pm and will take 5hrs to reach at 1).
D = 10 * t = 10 * 6 = 60.
Speed = 60/5 = 12.
Speed = 10.
Time = t.
Distance = 10 * t -----> (1).
2nd case.
Speed = 15.
Time = t - 2 (he reach at 2pm at t time so take t-2 for 12pm).
D = 15 * (t - 2) -----> (2).
From 1 and 2.
10 * t = 15 * (t - 2).
15t - 10t = 30.
t = 6.
So he need 5hrs to reach at 1pm (take 6hrs to reach 2pm and will take 5hrs to reach at 1).
D = 10 * t = 10 * 6 = 60.
Speed = 60/5 = 12.
Suma said:
9 years ago
If two distance is equal, here two distance is equal.
Then speed = 2s1s2/s1 + s2.
2 * 10 * 15/(10 + 15) = 12.
Then speed = 2s1s2/s1 + s2.
2 * 10 * 15/(10 + 15) = 12.
(1)
Vinaykumar said:
9 years ago
Simple :.
2 speeds calculate average speed 2xy/(x + y).
So,
2 * 10 * 15/(10 + 15).
12km/hr.
2 speeds calculate average speed 2xy/(x + y).
So,
2 * 10 * 15/(10 + 15).
12km/hr.
Naveen said:
9 years ago
Can anyone explain in easy way? It is hard to understand.
K.NAVEENA said:
9 years ago
2xy/(x + y) = [(2 * 10 * 15)/(10 + 15)] = 12kmph.
Marco said:
9 years ago
The average speed :
2*10*15/10 + 15.
= 300/25.
= 12 km/h.
2*10*15/10 + 15.
= 300/25.
= 12 km/h.
Kuru said:
1 decade ago
@Amir that was nice, and easy step to solve.
Thanks.
Thanks.
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