The tail of a 1-mile long train exits a tunnel exactly 3 minutes after the front of the train entered the tunnel. If the train is moving 60 miles per hour, how long is the tunnel?
Why is this wrong???
Let d be the length of the tunnel. Let the time that the train goes through this tunnel be t. Then d/t = 60, so d = 60t.
The train goes through d + 1 miles in t + 3/60 hours. So (d + 1)/60 = t + 3/60.
But this is wrong since it has no solutions. Why?!?!
When the front of the train enters, the tail has 1 mile to go to enter
(1 mile + length of tunnel ) / 60 = 3/60 hr (3/60 hr = 3 minutes)
tunnel length = 2 miles