Amir paid $4.50 for 2 pounds of grapes. What is the unit rate for 1 pound of grapes?

The answer is 2.25 because it is half

Since you're buying half as many grapes going down from 2 pounds to 1 pound, it makes sense that it should only cost half as much. Half of $4 is $2, and half of $0.50 is $0.25, so the unit rate for the grapes is $2.25 per pound.