The instructions state that Cheryl needs 3/8 square yards of one type of material and 1/3 square yards of another type of material for a project. She buys exactly that amount. After finishing the project, however, she has 15/40 square yards left that she did not use. What is the total amount of square yards of material Cheryl used?
Choose the correct choice from the following choices
A) 1 / 12	B) 1 / 9	C) 2 / 3	D) 1 / 3	E) 2 1 / 9

Rationale: "total bought = 3 / 8 + 1 / 3 left part 15 / 40 - - - > 3 / 8 so used part 3 / 8 + 1 / 3 - 3 / 8 = 1 / 3 ans d"
Answer: D