JIPMAT 2021 (QA) - A train with 90 kmph crosses a bridge in 36 s. Another train 100 m shorter crosses the same bridge at 45 kmph. The time taken by the second train to cross the bridge will be | PYQs + Solutions

JIPMAT 2021

Arithmetic

Time, Speed & Distance

Conceptual

A train with 90 kmph crosses a bridge in 36 s. Another train 100 m shorter crosses the same bridge at 45 kmph. The time taken by the second train to cross the bridge will be

60 s

64 s

68 s

72 s

Correct Option: 2

Let length of first train =

L

\newline

and Length of bridge

=B

For first train:

Length of train

+

bridge = Speed

×

Time

\newline

L + B = 90 × \frac{36}{3600}

km (an hour has 3600 seconds)

\newline

L + B = 0.9

km = 900 m --> Eq. 1

Let length of first train =

L

\newline

Then length of second train =

(L - 100)

For second train:

\newline

(L - 100) + B = 45 × \frac{t}{3600}

meters

\newline

Where

t

is time in seconds

From (1):

B = 900 - L

Substituting:

\newline

(L - 100) + (900 - L) = \frac{45t}{3600}

800 = \frac{45t}{3600}

t = 64

Therefore, second train takes 64 seconds.