Two minutes. It takes the front of the train one minute and the rest of the train will take two minutes to clear the tunnel.

1 1/2.

9

Pi (Pie)

Do you want to hear my problems?

Add two matches to make a roman numeral eight. ( VIII )

Drop the "S"

Because it had so many unsolved problem

Give them, 1 fifty dollar bill, 1 twenty dollar bill, 1 five dollar bill and 4 two dollar bills.

To the corner because it is 90 degrees.