Consider the question. There were 40 kids on Lake Pleasant. A fourth of the kids went tubing, but only half of the tubers went rafting. How many of the kids who joined the rafting excursion were also on the tubing excursion?
 If the answer is '5'; explain the reasoning:
40 / 4 = 10 kids went tubing. 10 / 2 = 5 kids went rafting and tubing.