(a) Hans bought 11 pounds of rice for $5.
How many dollars did he pay per pound of rice?
the unit price is given by the total price divided by the total weight, therefore:
He payed $0.45 per pound of rice
(b) It takes 16 pounds of seed to completely plant a 3-acre field.
How many pounds of seed are needed per acre?
the pounds of seed per unit area is given by the total pounds used to plant the total acres
so, the answer is 5.33 pounds per acre