Charlie bought a 2and 1 half bag of oranges for $3.75. What is the cost of one pound of oranges?

Let number be "x" (the cost of one pound of oranges);

(2 1 / 2) x = 3.75;

(5 / 2) x = 375 / 100;

x = (375 / 100) * (2 / 5);

x = 750 / 100;

x = $7.50;

Charlie buys 2.5 pounds of oranges for 3.75.

To find out how much he will pay for 1 pound of oranges, use the proportion

2.5/3.75 = 1/x

Cross multiply to get x = $1.50 per pound of oranges.