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 4 of 10.
Bikash Mahato said:
8 years ago
Let the distance has been travelled be x km.
At the speed of 10 kmph, it will reach 2pm.(equation 1.)
At the speed of 15, it will reach at 12 noon.(equation 2)
And,
At the speed of ?, it will reach at 1pm. (equation 3)
Let's balance the equation.1 and 2,
x/10-x/15=2 hours,
i.e. x=60km.
Now again balance the equation 2 and 3,
60/?-60/15=1 hours,
?=12,
Thus, 12 kmph is the answer.
At the speed of 10 kmph, it will reach 2pm.(equation 1.)
At the speed of 15, it will reach at 12 noon.(equation 2)
And,
At the speed of ?, it will reach at 1pm. (equation 3)
Let's balance the equation.1 and 2,
x/10-x/15=2 hours,
i.e. x=60km.
Now again balance the equation 2 and 3,
60/?-60/15=1 hours,
?=12,
Thus, 12 kmph is the answer.
Tirtha said:
8 years ago
If speed is 10 then he will reach at .2.
If speed 15 then he will reach at 12.
so for 1 pm then we can take avg (10+15)/2=12.5 aprox 12.
Is this correct?
If speed 15 then he will reach at 12.
so for 1 pm then we can take avg (10+15)/2=12.5 aprox 12.
Is this correct?
ELANAGAI said:
8 years ago
How did 60/10 came in the last? Can anyone explain after that?
Rinn sailo said:
8 years ago
Just take average speed.
Required speed.
= 2xy/(x+y),
=(2 x 10 x 15)/(10+15),
= 300/25.
= 12Km/hr.
That's it.
Required speed.
= 2xy/(x+y),
=(2 x 10 x 15)/(10+15),
= 300/25.
= 12Km/hr.
That's it.
Ishwarya said:
7 years ago
What is the logical and easiest method for solving this problem?
Revant said:
5 years ago
Clear solution. Thank you so much @Ankit.
Raman Sharma said:
7 years ago
Distance = speed * time.
For time ,let say time taken to travel to point A = t.
d = 15*t ------- eqn.1
d = 10(t+2) ------eqn. 2
d = s* (t+1)--------- eqn. 3.
From eqn 1 and eqn 2
15* t = 10(t+2).
after solving, t = 4 means time to travel is 4 hours.
now,
we put value of t = 4 in eqn 3 and eqn. 2.
60 = s(4+1).
s = 12 kmph.
For time ,let say time taken to travel to point A = t.
d = 15*t ------- eqn.1
d = 10(t+2) ------eqn. 2
d = s* (t+1)--------- eqn. 3.
From eqn 1 and eqn 2
15* t = 10(t+2).
after solving, t = 4 means time to travel is 4 hours.
now,
we put value of t = 4 in eqn 3 and eqn. 2.
60 = s(4+1).
s = 12 kmph.
Bhushan suriya said:
7 years ago
Consider starting time as x.
We know that time = (distance/speed),
When he reach at 2 P.M i.e.,14.00 (railway time)
(14-x) = (distance/ 10)
When he reach at 12 P.M
(12-x) = (distance/15)
As we know that., distance is the same.
So, from above equations we get x=8. so he started cycling at 8 A.M.
So from this, we can calculate distance = 60 km.
To reach at 1 P.M, the time taken is 5 hrs.
Speed = (60/5) = 12 kmph.
We know that time = (distance/speed),
When he reach at 2 P.M i.e.,14.00 (railway time)
(14-x) = (distance/ 10)
When he reach at 12 P.M
(12-x) = (distance/15)
As we know that., distance is the same.
So, from above equations we get x=8. so he started cycling at 8 A.M.
So from this, we can calculate distance = 60 km.
To reach at 1 P.M, the time taken is 5 hrs.
Speed = (60/5) = 12 kmph.
Subash said:
7 years ago
Thanks for the answer @Raja.
Shivasai said:
6 years ago
Then, x/10 - x/15 = 2 why we have taken this?
What is the logic behind it
What is the logic behind it
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