Value-Mart is advertising a Back-to-school sale on pencils. A pack of 30 sells for $7.97, whereas a 12-pack of the same brand cost for $4.77. Which is the better buy? How do you know?
You can see that the price of the first pack is less than twice the price of the second whereas you get lot more than twice much more pencils for it (30>24) so the first deal is clearly way better.