Correct Option: C

Trains are running in opposite direction.
∴  Relative speed of the two trains
= 90 + 60 = 150 km per hr.

Distance travelled in 4	1	seconds
	2

with speed of 150 km per hr.

= 150 ×	5	m per sec.
	18

= 150 ×	5	×	9
	18		2

=	375	metres
	2

Let the length of the first train be x metres.

Then the length of the second train be	x	metres
	2

∴   x +	x	=	375
	2		2

⇒	3x	=	375
	2		2

⇒  3x = 375
⇒  x = 125 metres
Hence, the length of the first
train = 125 metres
Speed of the first train = 60 km per hr.

= 60 ×	5	m per sec.
	18

=	50	m per sec.
	3

Time taken by the first train to cross the tunnel = 4 minutes

and 37	1	sec.
	2

= 240 +	75	sec. =	480 + 75
	2		2

=	555	sec.
	2

Speed of first train =	50	m per sec.
	3

∴  Distance covered by it in	555	sec.
	2

=	50	×	555	= 4625 metres
	3		2

Hence, length of tunnel
= 4625 – 125 = 4500 metres
= 4.5 km