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:
95 comments Page 10 of 10.
Mohamed said:
2 decades ago
This is another way of doing it:
In the last step what you can do instead is (60 / S) - (60 / 15) = 1 following the same logic as the predecessor example while S is the speed that will be arriving @ 1pm.
This will bring us to (900 - 60S) / 15S = 1
-> multiply this two sides to 15S, this will reap 15S = 900 - 60S.
then 75S = 900, S = 12 km/hr.
In the last step what you can do instead is (60 / S) - (60 / 15) = 1 following the same logic as the predecessor example while S is the speed that will be arriving @ 1pm.
This will bring us to (900 - 60S) / 15S = 1
-> multiply this two sides to 15S, this will reap 15S = 900 - 60S.
then 75S = 900, S = 12 km/hr.
Ashish said:
2 decades ago
Actually 5 comes as:
Robert start travelling at 8 am. Now difference between 8 am to 1 pm is 5 hrs.
So that 60/5.
Robert start travelling at 8 am. Now difference between 8 am to 1 pm is 5 hrs.
So that 60/5.
Das said:
2 decades ago
Hi, could u tell me why we have done 60/5 in last step ?
Xyz said:
2 decades ago
Its 2 hours
12 noon to 2pm = 2 hours
12 noon to 2pm = 2 hours
Arunkumar said:
2 decades ago
How to find that 2. We don't know the starting time. Then how that is calculated.
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