# Buying Protein Bars and Magazines

Alignments to Content Standards: 7.RP.A.3

Tom wants to buy some protein bars and magazines for a trip. He has decided to buy three times as many protein bars as magazines. Each protein bar costs \$0.70 and each magazine costs \$2.50. The sales tax rate on both types of items is 6½%. How many of each item can he buy if he has \$20.00 to spend? ## Solutions Solution: Using a ratio table The table below shows the cost for the protein bars and magazines in a 3 : 1 ratio.  Number of magazines 1 2 3 4 Number of protein bars 3 6 9 12 Value of the magazines \$2.50 \$5.00 \$7.50 \$10.00 Value of the protein bars \$2.10 \$4.20 \$6.30 \$8.40 Value of both magazines and candy bars \$4.60 \$9.20 \$13.80 \$17.40 Cost with tax \$4.90 \$9.80 \$14.70 \$19.60 Looking at the last column of the table, we can see that Tom can buy 4 magazines and 12 protein bars for \$20 and that he cannot afford 5 magazines and 15 protein bars.
The cost of a unit then is \$2.50 + 3$\times$(\$0.70), which is \$4.60. With sales tax, this would be \$4.60 $\times$ 1.065, which when rounded to the nearest cent would be \$4.90, or just under \$5.00.
There are four groups of five in 20 and 4 $\times$ 4.899 = 19.596. This leaves \$0.40 in change. So, with \$20, he can buy 4 magazines and 12 protein bars, with \\$0.40 in change.