late to class physics question

Question

It normally takes you 11.5 minutes to travel the 6 miles to COD along a straight road. You leave 13 minutes before Physics 2111 class begins. Delays caused by a broken traffic light slow down the traffic to 18.77 miles/hour for the first 2.5 miles.

1)How late will you be for class?

(If you will be late for class, type in a positive number. If you will be early, type in a negative number.)

Answer 1

Slow journey :

First 2.5 miles : 18.77 miles per hour. So will take (2.5 / 18.77) hours = (2.5 x 60 / 18.77) minutes

Remaining 3.5 miles : Normal speed is 6 miles in 11.5 minutes. So 1 mile in 11.5 / 6 minutes, so 3.5 miles in (3.5 x 11.5) / 6 minutes

So just add up the 2 times here, and compare to the 13 minutes you have.

MIKE