In order to find the price per bar, we divide the price by the amount of bars. For the first one:
15.37/10 = $1.54 per bar
The second package:
15.35/12 = $1.28 per bar.
The 10-pack costs $1.54 per bar and the 12-pack costs $1.28 per bar. The 12-pack has the better price per bar.
Now, let's look at the price per ounce. We do this in a similar way. We find the total amount of ounces in the package, and divide the price by the number of ounces.
In the first package, we multiply 10*2.1=21. We have 21 ounces in the first package. Now we divide 15.37/21. In the first package, we have 0.73 dollars per ounce.
Now, let's look at the second package. We start by multiplying 1.4*12=16.8. There are 16.8 ounces in the package. Now, we divide 15.35/16.8=0.91. So, in the second package, we have 0.91 dollars per ounce.
The cost per ounce of the 10-pack is $0.73 and the cost per ounce of the 12-pack is $0.91. The first package has the better price per ounce.
The better explanation is the second one, because I prefer the lower price per ounce, I think that the 1st pack is the better buy.
