Compare unit prices to determine the better value.
Free, timed SHSAT practice sets on unit pricing & best buy— every question includes a full worked explanation, and there's no account required.
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To find the better buy, compare the price for one unit (one ounce, one pound, one pencil).
\(\text{unit price} = \text{price} \div \text{quantity}\)
Example: 4 granola bars for 3.80 dollars is \(3.80 \div 4 = 0.95\) dollars per bar. 12 bars for 3.60 dollars is \(3.60 \div 12 = 0.30\) dollars per bar. The 12-pack is the better buy, even though both boxes cost about the same.
If the question asks what a larger amount costs, multiply the lower unit price by the amount you need.
Traps:
Unit price A \(= \$15.60 \div 8 = \$1.95\); unit price B \(= \$7.50 \div 6 = \$1.25\). The lower one is \(\$1.25\) per pound. (Picking the other package's price per unit (the higher one) gives $1.95. Dividing size by price (\(6 \div 7.50\)) gives $0.80. Reporting the cheaper package's total price gives $7.50.)
Unit price A \(= \$4.95 \div 11 = \$0.45\); unit price B \(= \$4.80 \div 2 = \$2.40\). The lower one is \(\$0.45\) per ounce. (Picking the other package's price per unit (the higher one) gives $2.40. Dividing size by price (\(11 \div 4.95\)) gives about $2.22. Dividing that package's price by the other package's size (\(\$4.95 \div 2\)) gives about $2.48.)