Aptitude - Time and Distance - Discussion

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.

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.

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.

5S=60.
S = 12kmph.

Time reached -- time taken -- Speed
2 p.m. -- t -- 10 km/hr
12 noon -- t-2 -- 15 km/hr
1 p.m. -- t-1 -- ?.

Distance is constant.
Writing in terms of time and speed, t x 10 = (t-2) x 15 which gives t = 6.
Distance is 60 km, so speed required to reach in t-1= 5 hrs i.e. at 1 p.m. is 60/5 = 12 km/hr.

Solution:

2xy/x+y >this is a formula.
2(10)(15)/10 + 15.
300/25 = 12kmph.

Thank you @Neha.

Clear solution. Thank you so much @Ankit.

As the time is in AP.
Speeds are in HP.

15kmph ---> 12 pm
X kmph ---> 1pm
10kmph ---> 2 pm.

HP = 2 * 15 * 10/15 + 10,
=300/25,
=12kmph.

@Vani.

If you want to reach at 1 P. M. Then from 8 o'clock to 1 the time comes out to be 5 hrs so we have taken 5hrs and from that we got speed.

@Bhushan suriya.

How 5 hours will get at the last at 1:00pm?