Easy Time, Speed & Distance Solved QuestionAptitude Discussion

 Q. A train starts from Delhi at 6:00 am and reaches Ambala cantt. at 10am. The other train starts from Ambala cantt. at 8am and reached Delhi at 11:30 am, If the distance between Delhi and Ambala cantt is 200 km, then at what time did the two trains meet each other?
 ✖ A. 8:46 am ✖ B. 8:30 am ✔ C. 8:56 am ✖ D. 8:50 am

Solution:
Option(C) is correct

Average speed of train leaving Delhi = $\dfrac{200}{4}=50$ km/hr

Average speed of train leaving Ambala cantt. = $200\times \dfrac{2}{7}=\dfrac{400}{7}$

By the time the other train starts from Ambala cantt, the first train had travelled 100 km

Therefore, the trains meet after:

$=\dfrac{200-100}{(50+400/7)}=\dfrac{14}{15}$hr

$=\dfrac{14}{15}\times 60=56$minutes

Hence they meet at 8:56 am

(5) Comment(s)

Suraj
()

Why do we multiply second train by 2/7?

Sirisha
()

400/3.5=400*2/7.......,where 3.5 is the time difference between 8am and & 11.30 am

()

Let t be the start time

A starts at t, while B starts at (t-2)

total distance covered is 200 km

as they are travelling in opposite direction,

relative dist covered

i,e 200=((200/4)*t )+((400/7)*(t-2))

t=176min

i.e 2hrs 56min from start (6 am)

therefore they meet at 8.56am.

Pree
()

$=\dfrac{100}{(50+400/7)}$

$=\dfrac{14}{15}$

and

$\dfrac{14}{15} \times 60 =56$

Deepak
()

Thanks Pree for the input, corrected now.