[email protected] wrote:A train M leaves Meerut at 5:00 am and reaches Delhi at 09:00 am. Another train N leaves Delhi at 07:00 am and reaches Meerut at 10:30 am. At what time do the two trains cross one another ?
(a) 8.26 am
(b) 8 am
(c) 7.36 am
(d) 7.56 am
Agree with Rich on questioning the source.
Assumption- trains travel at constant speed
First we have to find out where M is when N starts.
If M leaves at 5am and takes 4 hours to reach the end, at 7am M will be at half the distance traveled
Therefore we can rephrase the question to:
M and N leaves at 7am, what time do they meet?
distance = speed x time
distance M travels + distance N travels = total distance*(1/2)
(d/4)*t + (d/3.5)*t = d/2
t(d/4 + d/3.5) = d/2
t = (d/2) / (d/4 + d/3.5) = (d/2) / (2d/8 + 2d/7)
t = (d/2 / (30d/56) = (14/15)hr = 56minutes
Therefore total time = 56minutes + time they both started = 56minutes + 7am = 7.56
ans =
d
