Question

Two trains, having lengths 120 m and 100 m,
are running in the opposite direction with
velocities 40 km/h and 50 km/​

Answer 1

let the length of 1st train L1= 120m

length of 2nd train L2= 100m

speed of 1st train S1=40 km/hr

speed of 2nd train S2 = 50 km/hr

now formula is

speed= distance/ time

so,

S1 + S2 = (L1 + L2)/ time

(40 + 50) km/hr = (120+100) m/ time

90km/hr= 220m/time

now convert the speed from km/hr to m/s by multipying 5/18

90*5/18 km/hr = 220m/ time

25km/hr= 220m/time

time= 220/ 25= 8.8s

Answer 2

8.8s

Explanation:

total distance=120+100

=220

40km/h=40×5/18m/s

=200/18

50km/h=50×5/18m/s

=250/18

time required to cross the trains each other=total distance÷sum of speed of trains

200/18=100/9

250/18=125/9

100/9+125/9=225/9

=25m/s

sum of speed of trains=25m/s

220÷25=8.8s