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.
Abishek jesuraj said:
7 years ago
Well I would make it simple !!
first, let us find the time (in hrs)
let t be the time
distance/speed = time, distance we don't know so take it as x.
here there are two references given with respect to time.
he once reached at 2pm which can be taken as t .
he again reached at 12pm so that can be taken as t - 2.
So now there are two times , (t) and (t-2).
substitute this in formula (above distance\speed = time).
x/10 - x/15 = (t) - (t-2) (difference of two times, two distances etc),
now, (15x - 10x) / 150 = 2,
5x = 300,
x=60km.
Now we have found the distance travelled
Again substitute this in formula
speed = d/t.
1st case
10= 60 / t = 6hrs.
2nd case
15 = 60 / t = 4hrs
so if in the frst case he has travelled for 6 hours and reached at 2pm. so he would have started at 8am.
Now the main problem, at what speed he must travel so that he can reach at 1pm?
he starts at 8 am and he should reach at 1 pm so his travel must be 5 hrs.
Now substitute 5hrs in the formula speed =d/t.
speed = 60/5,
speed = 12 kmph.
first, let us find the time (in hrs)
let t be the time
distance/speed = time, distance we don't know so take it as x.
here there are two references given with respect to time.
he once reached at 2pm which can be taken as t .
he again reached at 12pm so that can be taken as t - 2.
So now there are two times , (t) and (t-2).
substitute this in formula (above distance\speed = time).
x/10 - x/15 = (t) - (t-2) (difference of two times, two distances etc),
now, (15x - 10x) / 150 = 2,
5x = 300,
x=60km.
Now we have found the distance travelled
Again substitute this in formula
speed = d/t.
1st case
10= 60 / t = 6hrs.
2nd case
15 = 60 / t = 4hrs
so if in the frst case he has travelled for 6 hours and reached at 2pm. so he would have started at 8am.
Now the main problem, at what speed he must travel so that he can reach at 1pm?
he starts at 8 am and he should reach at 1 pm so his travel must be 5 hrs.
Now substitute 5hrs in the formula speed =d/t.
speed = 60/5,
speed = 12 kmph.
Ishwarya said:
7 years ago
What is the logical and easiest method for solving this problem?
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.
ELANAGAI said:
8 years ago
How did 60/10 came in the last? Can anyone explain after that?
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?
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.
Ranjith said:
8 years ago
How you are saying starting 8am @Ashish.
Sagar said:
8 years ago
8 am to 1 pm= 5 hours.
Distance:-60 and time:-5.
Therefore: 60/5 is taken at last step.
i.e: speed:-distance/ time.
Distance:-60 and time:-5.
Therefore: 60/5 is taken at last step.
i.e: speed:-distance/ time.
Aarusi said:
8 years ago
It can be solved easily by applying the average speed formula:
x = 10(given)(speed)
y = 15(given)(speed)
For average speed:
2xy/x + y
2 * 10 * 15/10 + 15 = 12.
x = 10(given)(speed)
y = 15(given)(speed)
For average speed:
2xy/x + y
2 * 10 * 15/10 + 15 = 12.
Prawesh Pradhan said:
8 years ago
After finding the distance.
60/10-60/x = 1,
6x-60 = x,
5x = 60,
x = 12.
60/10-60/x = 1,
6x-60 = x,
5x = 60,
x = 12.
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