Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 1 - Problem Solving and Critical Thinking - 1.3 Problem Solving - Exercise Set 1.3 - Page 38: 9


a. The second box of cereal is more value. b. The first box is $\$0.22$ per ounce, the second box is $\$3.06$ per pound. c. No.

Work Step by Step

a. The first box of cereal weighs $15.3$ ounces and costs $\$3.37$. The second box weighs 24 ounces and costs $\$4.59$. Out of these two, we calculate which one is a better value by dividing the cost by the weight and getting a number which represents how much we pay for each ounce of cereal, in both cases. $3.37\div15.3\approx0.22$ (dollars per ounce) $4.59\div24\approx0.19$ (dollars per ounce) We can clearly see that the second box of cereal is a better value, as you pay less for an ounce of cereal. b. We've already determined unit price in terms of cost per ounce for the first box, and it's $\$0.22$ per ounce. To get the unit price in terms of cost per pound for the second box, we first need to convert its weight from ounces to pounds: $24\div16=1.5$ (pounds) Then calculate the unit price by dividing the cost of the box by the weight of the box. $4.59\div1.5=3.06$ (dollars per pound) c. The better value doesn't necessarily have the lower displayed unit price, because the unit might be different, and as we saw in the example of this store, the displayed price per unit for the second box is greater, because the unit is pounds, instead of ounces, but the second box is actually the better value, when we calculate the price per unit for both boxes in ounces.
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