Bunuel wrote:

Official Solution:

The train consists of 6 carriages, 20 meters long each. The gap between the carriages is 1 meter. If the train is moving at a constant speed of 60 km/h, how much time will it take the train to run through a 1 kilometer tunnel?

A. \(1\frac{1}{8}\) minutes

B. \(1\frac{1}{2}\) minutes

C. \(1\frac{3}{4}\) minutes

D. 2 minutes

E. \(2\frac{1}{4}\) minutes

The length of the train is \(6*20\) plus five 1 meter gaps, so it's \(6*20+5=125\) meters;

The length that should be traveled by train is \(1+0.125=1.125\) kilometers;

\(\text{Time}=\frac{\text{Distance}}{\text{Rate}}=\frac{1.125}{60}\) hours or \(\frac{1.125}{60}*60=1.125=1\frac{1}{8}\) minutes.

Answer: A

Hi Bunuel,

Your question is a little bit ambiguous.

When one say that the train is entering into tunnel, the total time train was inside the tunnel is the time taken by the train when 1st coach enters the tunnel till the last coach exits the tunnel.

That makes 1 km + 125 + 125.

I don't know why did you pick 1 km + 125 m ?

Can you please clarify?