Easy Time, Speed & Distance Solved QuestionAptitude Discussion

 Q. Two stations $A$ and $B$ are 110 km apart on a straight line. One train starts from $A$ at 7 am and travel towards $B$ at 20 km/hr speed. Another train starts from $B$ at 8 am and travel towards $A$ at 25 km/hr speed. At what time will they meet?
 ✖ A. 9 am ✔ B. 10 am ✖ C. 11 am ✖ D. None of these

Solution:
Option(B) is correct

In 1 hour (7 am to 8 am) tarin from station A travels 20 km distance and reaches to $C$, (say).

$A$ ----------------- $C$ ---------------$B$
7 am --------------------------------- 8 am

$AC$ = 20 km, $CB$ = 90 km

Distance travelled in 1 hour = 20 km

Remaining distance =$110−20$ = 90 km

$\text{Time}=\dfrac{\text{Distance}}{\text{Speed}}$

$\dfrac{90}{20+25}=2$ hours

So, time = 8 am + 2 am = 10 am

(7) Comment(s)

Imran
()

Why do we add $2$ hours with that of second train's starting time?

Are we not supposed to add with the firsts'?

Shireen
()

Hey Imran, time is added AFTER $A$ has traveled for 1 hour (i.e. time is 8 AM now). Now it takes two more hours after 8 AM when both $A$ and $B$ travel at the speed of 20 km/hr and 25 km/hr respectively.

That is why 2 hours time is added after 8 AM and not 7 AM, it has nothing to do with the first or second train's time.

Hope that helps :)

Imran
()

thanks shireen..i got it..

()

Thank you, Aman, now I got it

Aman
()

Pleasure is all mine, Madhu :)

Train from station $B$ starts AFTER 1 hour (at 8 am). So in that time, train from station $A$ travels till point $C$ for 1 hour, with the speed of 20 km/hr. Which makes distance $AC=20$ km.