Tod woke up late and had to rush to school. He lives on an island and missed the school boat. Consequently he took his own motorboat and drove it fast - 15 knots per hour. The trip took 20 minutes. How far did he go.

Distance = Rate x Time.

So, now I'll solve the problem

Distance is the question - D
Rate is the speed - 15 knots per hour
Time is 20 minutes. - 1/3 of an hour.

D = 15 x 1/3 = 5 knots.