Question

McDonalds sells quarter-pound cheeseburgers for .99 cents last saturday.they sold 310 of these cheeseburgers. how many pounds of cheese did they sell last saturday?

Answer 1

The first thing you should do is calculate how many pounds of cheese a hamburger has
 1 hamburger = 1/4 pound of cheese.
 Then, you can make a rule of three to know how many pounds of cheese were sold:
 1 ---> 1/4
 310 ---> x
 Clearing x we have:
 x = ((310) / (1)) * (1/4) = 77.5
 Answer
 they sell last saturday 77.5 pounds of cheese