Aptitude - Time and Distance - Discussion

Discussion Forum : Time and Distance - General Questions (Q.No. 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.?
8 kmph
11 kmph
12 kmph
14 kmph
Answer: Option

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.

So, Robert started 6 hours before 2 P.M. i.e., at 8 A.M.

Required speed = 60 kmph. = 12 kmph.

90 comments Page 1 of 9.

Vivek said:   4 months ago
Case1: speed = 10kmph.
Ce2: speed = 15kmph.
Given d/10-d/15 = 2,
case1 time=60/10, time=6,
case2 time=60/15, time=4,

so, for 12noom time is 4, and for 2 pm is 6
And 1 pm is between them so it will be 5.

And 60/5=12.

Anushree Kulkarni said:   2 years ago

Best and neat explanation, Thank you.

Anuj said:   2 years ago
10 kmph (2 pm) = t h ----> eq(1)
x kmph (1 pm) = (t-1)h ----> eq(2)
15 kmph (2 pm) = (t-2)h ----> eq(3)
Since, distance is the same for all cases we can equate these equations to get the answer.

Vicky said:   3 years ago
How 3 came? Please explain.

Akash said:   3 years ago

Use formula like (2 (a.b) /a+b) a is speed 10kmph and b is 15kmph.

Hope you get it.

Prathamesh Pendal said:   3 years ago
1pm is in between 12 and 2 pm.
So, if we find average speed we can also get the answer.
Avg speed = (2*15*10)/(10+15) = 12.

Havoc said:   3 years ago
We can also use average speed formula.

Because 12 am to 2 pm time 2 hr.
Thus 12 am to 1 am 1 hr.
So, we can find use avg speed also,
The mid point time of 12 am and 2 pm is 1 pm.

Farzana said:   4 years ago
Let the distance be x.

According to statement 1.
If he travels at 10 kmph and let's imagine the time taken to reach at 2 pm is 't' hrs

i.e, x/10=t ---> equation(1).

According to statement 2.

If he travels at 15 kmph and reaches at 12 noon, then he reaches 2 hrs earlier than the previous time (i.e, t-2 hrs)

then, x/15=t-2 ------> equation(2)

If you get two equations with same two variables, always subtract one equation from the other.

Here, the equations become,
x/10-x/15=t-(t-2) or x/15-x/10=(t-2)-t
either way you will get the same answer i.e, x=60 km.

Just Put this in equation(1) or equation(2) and you will get the original time.
equation(1), 60/10=t, t=6.
equation(2), 60/15=t-2, 4=t-2, t=6.

So if Robert wants to reach the destination at 1 pm, We have to calculate his speed, we got distance and time taken.

If he wants to reach at 1 pm which is 1 hr less than the normal time.
then equation becomes distance/speed=time-1 hr.

i.e, 60/speed=6-1, speed=60/5, speed=12 kmph.
Therefore, the answer is 12 kmph.

Ritik Florian said:   4 years ago
Simply, find the average speed u can get the answer. Since 1 pm comes between 12 noon and 2 pm.

The formula for finding AVG speed is= 2xy/X+y.
i.e. 2*10*15/10+15= 12.

Ishwar said:   4 years ago
Let calculate distance firs say d.

D/10-d/15=2 (he reach 12noon 2hr early).

By calculating we get d = 60km.

Let's speed is S to calculate S difference between travel at first speed rate and S rate is.
60/10-60/S=1 (because he reaches by 1 am, 1hr early).

By calculating this we get.

S = 12kmph.

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