Difference between revisions of "2007 AMC 10A Problems/Problem 5"

Revision as of 14:22, 6 January 2008

Problem

A school store sells 7 pencils and 8 notebooks for $$$$ $4.15$ . It also sells 5 pencils and 3 notebooks for $$$$ $1.77$ . How much do 16 pencils and 10 notebooks cost?

$\text{(A)}\$ $1.76 \qquad \text{(B)}\$ $5.84 \qquad \text{(C)}\$ $6.00 \qquad \text{(D)}\$ $6.16 \qquad \text{(E)}\$ $6.32$

Solution

We let $p =$ cost of pencils in cents, $n =$ number of notebooks in cents. Then

$\begin{align*} 7p + 8n = 415 &\Longrightarrow 35p + 40n = 2075\\ 5p + 3n = 177 &\Longrightarrow 35p + 21n = 1239 \end{align*}$

Subtracting these equations yields $19n = 836 \Longrightarrow n = 44$ . Backwards solving gives $p = 9$ . Thus the answer is $16p + 10n = 584\ \mathrm{(B)}$ .

2007 AMC 10A (Problems • Answer Key • Resources)
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Difference between revisions of "2007 AMC 10A Problems/Problem 5"

Revision as of 14:22, 6 January 2008

Problem

Solution

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