A food company stores grain in a hopper. The hopper is 12 feet in diameter and holds 2024.5 cubic feet of grain. When turned on, the hopper empties grain at a constant rate of 42 cubic feet per second. About how long does it take for the hopper to empty all the grain?

A patient is to receive medication at the rate of 0.45mg per kilogram of body weight. How many milligrams will you administer if the patient weighs 50kg?

A theme park company is building a scale model of a 84,780 cubic feet killer whale tank. Each dimension will be made 5 times smaller to accommodate the mock-up in the presentation room. How many times smaller than the actual volume is the volume of the mock-up?

Initially a tank contains 10 liters of pure water. Brine of unknown (but constant) concentration of salt is flowing in at 1 liter per minute. The water is mixed well and drained at 1 liter per minute. In 20 minutes there are 15 grams of salt in the tank. What is the concentration of salt in the incoming brine?