Q. If I need to cook rotini pasta to end up with 8 pounds of cooked pasta, how much uncooked pasta do I need to buy?
This sounds like one of the despised word problems from seventh-grade math. We never felt entirely comfortable with those word problems, but we'll give it a try. A pound of uncooked dried pasta generally yields about 3 pounds of cooked pasta, so you need about 2-2/3 pounds of dried pasta. Three pounds of cooked pasta will serve about 5 for a main course, so your 8 pounds will serve 13 people.
A pound of fresh pasta, by the way, yields 2 to 2-1/2 pounds of cooked pasta.