A company makes concrete bricks shaped like rectangular prisms. Each brick is 15 inches long, 10 inches wide, and 5 inches tall. If they use 15,000 in^3 of concrete, how many bricks did they make?
The volume of each brick is 15 in x 10 in x 5 in = <<15*10*5=750>>750 in^3.
Therefore, the number of bricks they made is 15,000 in^3 / 750 in^3/brick = <<15000/750=20>>20 bricks. Answer: \boxed{20}.