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 7 of 10.
Ajit said:
1 decade ago
We need to calculate the distance, then we can calculate the time and finally speed .
Lets solve this,
Let the distance travelled by x km.
Time = Distance/Speed.
x10-15 = 2[because, 2 pm - 12 noon = 2 hours] 3x-2x=60 =>x=60.
Time = Distance*Speed,
Time@10km/hr = 60/10 = 6 hours
So 2 P.M. - 6 = 8 A.M
i.e. Robert starts at 8 A.M.
He have to reach at 1 P.M.
i.e,diff between 8 A.M to 1P.M in 5 hours
So, Speed = distance/time => 60/5 = 12 km/hr
Lets solve this,
Let the distance travelled by x km.
Time = Distance/Speed.
x10-15 = 2[because, 2 pm - 12 noon = 2 hours] 3x-2x=60 =>x=60.
Time = Distance*Speed,
Time@10km/hr = 60/10 = 6 hours
So 2 P.M. - 6 = 8 A.M
i.e. Robert starts at 8 A.M.
He have to reach at 1 P.M.
i.e,diff between 8 A.M to 1P.M in 5 hours
So, Speed = distance/time => 60/5 = 12 km/hr
Vishu said:
1 decade ago
x/10-x/15=2
=>3x-2x=60
I didn't get the proper method.
How it comes anyone could tell me briefly it will be helpful for me.
=>3x-2x=60
I didn't get the proper method.
How it comes anyone could tell me briefly it will be helpful for me.
Venkat said:
1 decade ago
Thank you Raja.
Raja said:
1 decade ago
Simple one
2pm-12=2 hour
Similarly 15km-10km=5km
5km/2hour=2.5km/h
initial 10+2.5=12.5 nearer to 12
2pm-12=2 hour
Similarly 15km-10km=5km
5km/2hour=2.5km/h
initial 10+2.5=12.5 nearer to 12
Srinu said:
1 decade ago
Hi vyshu
2 is time between 12noon and 1pm why subtracting
12noon - 2 pm = 2 it is time
x/15-x/10=2 x=60km
12noon time =60/15=4hrs(before) mean 8am
find speed 1pm----------8am to 1pm time is 5 hrs ,distance 60km,speed =? speed=60/5= 12kmph
2 is time between 12noon and 1pm why subtracting
12noon - 2 pm = 2 it is time
x/15-x/10=2 x=60km
12noon time =60/15=4hrs(before) mean 8am
find speed 1pm----------8am to 1pm time is 5 hrs ,distance 60km,speed =? speed=60/5= 12kmph
Pardhu said:
1 decade ago
Thank you aamir. Is this applicable for all these type methods. ?
Santhosh said:
1 decade ago
How to solve the equation first?
Mohamed said:
1 decade 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:
1 decade 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:
1 decade ago
Hi, could u tell me why we have done 60/5 in last step ?
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