Train Travels Through Tunnel

Number Theory Level 2

A train traveling at a speed of 90 mph enters a tunnel 3.5 miles long. If the length of the train is 0.25 miles long, how long does it take for all of the train to pass through the tunnel from when the front enters to the moment the rear emerges?

2.5 min. 2.5 mmin 3 min. 2 min.

Selena Zheng by Selena Zheng , 15, USA

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1 solution

d = V t d=Vt where: d = distance, V = speed and t = time

0.25 + 3.5 = 90 t 0.25+3.5=90t

t = 1 24 hours = 2.5 minutes t=\dfrac{1}{24} \text{hours} = \color{#69047E}\large{\boxed{2.5 \text{minutes}}} answer \color{#3D99F6}\boxed{\text{answer}}

2 Helpful 0 Interesting 0 Brilliant 0 Confused

Here time will be counted from the time when the frontmost point of the train enters the tunnel to the point when the last point of the train exits the tunnel.

So,

DISTANCE = (LENGTH OF THE TUNNEL)+(2 × LENGTH OF THE TRAIN)

D = 3.5 + 0.5 = 4

TIME = D ÷ S = 4 ÷ 90 = (2/45)hours

(2/45)hours = 2.5 minutes

Aditya Shrivastava - 1 year, 4 months ago

I think you are wrong. Distance = length of tunnel + length of train = 3.5 + 0.25 = 3.75 miles

A Former Brilliant Member - 1 year, 4 months ago

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