Question

Two trains 135 m and 75 m long are running in
opposite directions with the speeds of 60 kmph
and 48 kmph respectively. How long will they
take to completely cross each other?
(a) a ser
(1.17​

Answer 1

Sᴏʟᴜᴛɪᴏɴ :-

Note :-

• when Two Trains cross Each Other, Distance the coveres in crossing is Equal to sum of Length of Both Trains.
• Speed is Add when they are in Opposite Direction.
• Speed is Reduced when they are in same Direction.

Given That :-

→ Length of first Train = 135m.

→ Length of 2nd Train = 75m.

→ Speed of first Train = 60km/h.

→ Speed of 2nd Train = 48km/h.

So,

→ Total Distance covered in crossing = 135 + 75 = 210m.

→ Usual Speed = 60 + 75 = 135km/h = 135 * (5/18) = (15 * 5)/2 = (75/2) m/s.

Therefore,

→ Time taken to cross each other = (Distance/speed) = 210/(75/2) = 210 * (2/75) = (14 * 2) / 5 = (28/5) = 5.6 seconds.(Ans.)

Hence, They will take 5.6 seconds to completely cross each other.

Answer 2

→ Given

→ Length of both train = 135m & 75m

→ speed of both trains = 60km/h & 48km/h

Solution

→Total distance = sum of length of both trian

→Total distance = 135+75

→Total distance = 210m

$\rule{230}2$

→ speed = 60+75

→ speed = 135km/h

now,

→change speed in m/s

so,

$\rightarrow\tt 135\frac{5}{18} \\\tt\rightarrow \frac{75}{2}$

Therefore,

→Time taken to cross each other .

we know,

$\tt\rightarrow time=\frac{Distance}{speed}$

$\tt\rightarrow time=\frac{210}{75}{2}\\ \tt \rightarrow time=\frac{210×2}{75}\\\tt\rightarrow time=\frac{420}{75}\\\tt\rightarrow time=5.6sec$

$\rule{130}2$

Hence,

$\tt\pink{\fbox{\fbox{time= 5.6sec}}}$