Question: As Dan is learning to screen-print t-shirts to sell at the craft fair, he makes t-shirts, over the first hour, at the rate of one every 12 minutes. Then, in the second hour, he makes one at the rate of every 6 minutes. How many t-shirts does he make over the course of those two hours? Think carefully first, then make a decision:
He made 60 / 12 = 5 the first hour. He made 60 / 6 = 10 the second hour. He made 5 + 10 = 15. So the answer is 15.