A train 1 mile long traveling at a const rate of 60mph takes how long to pass completely thru a 1 mile tunnel?

2 hours and 1 second.

The train must travel 2 miles as soon as it enters the tunnel to pass through completely. 60mph = 1 mile/minute, and so 2 miles = 2 minutes.

It has to travel 2 miles so it takes 1/30 of an hour

john v is right. 2 minutes

Just two minutes...

The train is going a mile a minute (60 miles per hour / 60 minutes per hour = 60 / 60 miles/minutes)
The front of the train enters the tunnel. One minute later, the front end exits the tunnel. Now the mile length of the train must exit, taking another minute.

So it is just two minutes.

rear of train is 1 mile from entrance of tunnel as train enters tunnel.
rear of train has to travel 2 miles to clear tunnel.
t = 2 / 60 h
t = 2 min