If you could buy a pack of 6 pencils for $7.50 and a pack of 10 pencils for $11, which one would you go for? Is the $7.50 pack cheaper than the $11 one? How do you know? When comparing the prices of different items, you must use the unit price of the objects. This free math activity demonstrates the importance of using proportions to determine the actual price of objects, instead of just looking at the total price of the pack.