Question: how many cups is 2 1/2 pounds of apples?
Answer: A pound of apples will yield 3 cups; so for 8 cups prepared apples, you'll need about 2 2/3 pounds whole apples (make it 2 3/4 pounds, if you're at the supermarket weighing). I tried this math with different sizes of apples; large apples yield slightly more prepared apples per pound than small apples.