A train with 90 km/hr crosses bridge in 36 seconds. Another train 100 metres shorter crosses the same bridge at 45 km/hr. Find the time taken by the second train to cross the bridge.
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A train with 90 km/hr crosses bridge in 36 seconds. Another train 100 metres shorter crosses the same bridge at 45 km/hr. Find the time taken by the second train to cross the bridge.
Answer
Let the distance of bridge = a
let the length of the first train = b
Then distance travelled by first train =a+b
Distance = speed × time
hence (a+b) =90×(5/18)×36
=25×36
=900 metres.
Give length of second train =b-100
Then total distance travelled by second train = a+(b-100)=45×(5/18)×t
a+b=25/2×t+100
by substituting above equation
900=25/2×t+100
800=25/2×t
t = 1600/25
t= 64 seconds.
Answer
Let the distance of bridge = a
let the length of the first train = b
Then distance travelled by first train =a+b
Distance = speed × time
hence (a+b) =90×(5/18)×36
=25×36
=900 metres.
Give length of second train =b-100
Then total distance travelled by second train = a+(b-100)=45×(5/18)×t
a+b=25/2×t+100
by substituting above equation
900=25/2×t+100
800=25/2×t
t = 1600/25
t= 64 seconds.
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