Difference between revisions of "2012 AMC 8 Problems/Problem 19"

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==See Also==
 
==See Also==
 
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Revision as of 15:38, 3 July 2013

Problem

In a jar of red, green, and blue marbles, all but 6 are red marbles, all but 8 are green, and all but 4 are blue. How many marbles are in the jar?

$\textbf{(A)}\hspace{.05in}6\qquad\textbf{(B)}\hspace{.05in}8\qquad\textbf{(C)}\hspace{.05in}9\qquad\textbf{(D)}\hspace{.05in}10\qquad\textbf{(E)}\hspace{.05in}12$

Solution

Let $r$ be the number of red marbles, $g$ be the number of green marbles, and $b$ be the number of blue marbles.

We have three equations:

$g + b = 6$

$r + b = 8$

$r + g = 4$

Now we use some algebraic manipulation.

We add all the equations to obtain a fourth equation:

$2r + 2g + 2b = 18$

Now divide by $2$ on both sides to find the total number of marbles:

$r + g + b = 9$. The total number of marbles in the jar is $\boxed{\textbf{(C)}\ 9}$.

See Also

2012 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
Problem 18
Followed by
Problem 20
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AJHSME/AMC 8 Problems and Solutions

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