# A train 360 m long is running at a speed of 45 km/hr. In what time will it pass a bridge 140 m long?

A. 40 sec

B. 42 sec

C. 45 sec

D. 48 sec

**Answer: Option A **

__Solution(By Examveda Team)__

$$\eqalign{
& {\text{Formula}}\,{\text{for}}\,{\text{converting}}\,{\text{from}}\,{\text{km/hr}}\,{\text{to}}\,{\text{m/s:}} \cr
& X\,{\text{km/hr}} = {X \times \frac{5}{{18}}} \,{\text{m/s}} \cr
& {\text{Therefore,}}\,{\text{Speed}} \cr
& = {45 \times \frac{5}{{18}}} \,{\text{m/sec}} = \frac{{25}}{2}{\text{m/sec}} \cr
& {\text{Total}}\,{\text{distance}}\,{\text{to}}\,{\text{be}}\,{\text{covered}} \cr
& = \left( {360 + 140} \right)m = 500\,m \cr
& {\text{Formula}}\,{\text{for}}\,{\text{finding}}\,{\text{Time}} \cr
& = {\frac{{{\text{Distance}}}}{{{\text{Speed}}}}} \cr
& \therefore {\text{Required}}\,{\text{time}} \cr
& = \left( {\frac{{500 \times 2}}{{25}}} \right)\,\sec \cr
& = 40\,\sec . \cr} $$
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## Comments ( 4 )

Related Questions on Problems on Trains

A. 120 metres

B. 180 metres

C. 324 metres

D. 150 metres

A. 45 km/hr

B. 50 km/hr

C. 54 km/hr

D. 55 km/hr

A. 200 m

B. 225 m

C. 245 m

D. 250 m

5/18 has come from 1000/3600

Eme Lamsal :

When km/hr is changes into m/s then we have

1km=1000m also 1hr=3600s now km/hr=1000/3600 we get 5/18

Eme Lamsal :

When km/hr is changes into m/s then we have

1km=1000m also 1hr=3600s now km/hr=1000/3600 we get 5/18

Will you explain me how 5/18 comes?