Product A is a 12-ounce bottle of generic popcorn oil that sells for $1.39. Product B is a 24-ounce popcorn oil bottle that costs $2.79. Which is the better buy?

Simply divide the price by the number of ounces to get the price per oz.

$1.39 : 12 = about $.1158 cents per oz

$2.79 = 24 = about $.11625 cents per oz.

By a very small amount the $1.39 bottle is a better deal.

You could also think that $1.39 for 12 oz is $2.78 for 24 (I doubled both numbers)

$2.78 for 24oz is a drop cheaper than $2.79 for 24 oz so $1.39 is a slightly better buy.