Answer:
B- 12 ounce box
Explanation:
You want to know which box of cereal is a better buy:
A- 20 ounces for $3.20
B- 12 ounces for $1.80
Comparison
There are several ways to compare prices. One is to find the unit price (price for 1 ounce) as in the attachment. This tells you the unit price for a 20-ounce box ($0.16/oz) is more than the unit price for a 12-ounce box ($0.15/oz).
The better buy is B- 12 ounce box.
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Additional comment
You can also use common multiples or common factors of the quantities to compare prices for the same quantity:
60 ounces of cereal = 3 20-oz boxes for $9.60, or 5 12-oz boxes for $9.00
2 ounces of cereal = 1/10 of a 20-oz box for $0.32, or 1/6 of a 12-oz box for $0.30
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