well, let's see the 10-pack is $15.37 BUT each of those 10 bars are 2.1 oz, so for the whole package you're getting really 10 * 2.1 = 21.0 oz.
the 12-pack costs $15.35 BUT each of those 12 bars are 1.4 oz, so for the whole package you're getting 12 * 1.4 = 16.8 oz.
which is the better deal? which one gives you more ounces for the money? after all, you're going to eat the bars, so you want more ounces, not more bars.
[tex]\bf \cfrac{15.37}{21}\cfrac{\$}{oz}~~\approx ~~0.73~\frac{\$}{oz}~\hspace{10em} \cfrac{15.35}{16.8}\cfrac{\$}{oz}~~\approx ~~0.91~\frac{\$}{oz}[/tex]
so clearly you'd want to get the cheapest one with more ounces, so at $0.73 or 73 cents for each ounce, the 10-pack is the cheapest.
