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?
He made 60/12=<<60/12=5>>5 the first hour.
He made 60/6=<<60/6=10>>10 the second hour.
He made 5+10=<<5+10=15>>15
#### 15