Aptitude - Problems on Trains - Discussion

Discussion Forum : Problems on Trains - General Questions (Q.No. 25)
25.
A train 108 m long moving at a speed of 50 km/hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is:
48 km/hr
54 km/hr
66 km/hr
82 km/hr
Answer: Option
Explanation:

Let the speed of the second train be x km/hr.

Relative speed = (x + 50) km/hr
= [ (x + 50) x 5 ] m/sec
18
= [ 250 + 5x ] m/sec.
18

Distance covered = (108 + 112) = 220 m.

Therefore 220 = 6
( 250 + 5x (
18

=> 250 + 5x = 660

=> x = 82 km/hr.

Discussion:
77 comments Page 4 of 8.

Ravi tomar said:   6 years ago
220m=0.220km : 6 sec = 1/600 hr.

0.220/ (50+x) = 1/600
0.220x600 = (50+x) => 132 = 50+x

x = 132-50=82,
x=82 km/hr.

Muthulakshmi said:   1 decade ago
Hai Mr.Ramesh

You are Correct.Thanks for explaining the problem clearly

MAHI said:   6 years ago
Here, time is in seconds & distance is in meters that's why we have to convert the speed into m/sec. Initially assume that X is in km/hr. SO we have to convert the speed in m/sec as all parameters is in meter & seconds. After solving where get the value of x in km/hr,

Swati hande said:   5 years ago
Thanks all for explaining.

Kajal said:   5 years ago
Why have we assumed x in km/he why not in m/s?


Please, someone, explain it.

Shubham said:   5 years ago
Thanks @Mahi.

Ambika said:   1 decade ago
Length of the trains=108+112=220m=(220/1000)=(11/50)km

Let the speed of second train be xkm/hr
therefore,relative speed=(50+x)km/hr(since it is opposite direction the speeds should be added)
time=6sec=(6/3600)=(1/600)hr
then solve using the formula time=(distance/speed)
i.e (11/50)/(50+x)=(1/600)
after solving x will be 82km/hr

Rakshikasaravanan said:   5 years ago
First train speed 50sec.

Second train speed?
S = l1 + l2/t1 + t2.
Relative speed = x + 50s.
X + 50s = 108+112/6+t2.
X + 50s =792/6.
6x + 300=792.
6x = 792-300.
6x = 492.
X = 492/6.
X = 82.

Gargi Banerjee said:   1 decade ago
Please give an appropriate answer with perticular reason, this is not clear to me.

Deepa Singh said:   1 decade ago
Please solve this part clearly 220/(5x+250)/18=6


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