Difference between revisions of "1986 AIME Problems/Problem 4"

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== Problem ==
 
== Problem ==
Determine <math>\displaystyle 3x_4+2x_5</math> if <math>\displaystyle x_1</math>, <math>\displaystyle x_2</math>, <math>\displaystyle x_3</math>, <math>\displaystyle x_4</math>, and <math>\displaystyle x_5</math> satisfy the system of equations below.
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Determine <math>3x_4+2x_5</math> if <math>x_1</math>, <math>x_2</math>, <math>x_3</math>, <math>x_4</math>, and <math>x_5</math> satisfy the system of equations below.
<center><math>\displaystyle 2x_1+x_2+x_3+x_4+x_5=6</math></center>  
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<center><math>2x_1+x_2+x_3+x_4+x_5=6</math></center>  
<center><math>\displaystyle x_1+2x_2+x_3+x_4+x_5=12</math></center>
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<center><math>x_1+2x_2+x_3+x_4+x_5=12</math></center>
<center><math>\displaystyle x_1+x_2+2x_3+x_4+x_5=24</math></center>
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<center><math>x_1+x_2+2x_3+x_4+x_5=24</math></center>
<center><math>\displaystyle x_1+x_2+x_3+2x_4+x_5=48</math></center>
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<center><math>x_1+x_2+x_3+2x_4+x_5=48</math></center>
<center><math>\displaystyle x_1+x_2+x_3+x_4+2x_5=96</math></center>
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<center><math>x_1+x_2+x_3+x_4+2x_5=96</math></center>
  
 
== Solution ==
 
== Solution ==
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[[Category:Introductory Algebra Problems]]
 
[[Category:Introductory Algebra Problems]]
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{{MAA Notice}}

Revision as of 19:04, 4 July 2013

Problem

Determine $3x_4+2x_5$ if $x_1$, $x_2$, $x_3$, $x_4$, and $x_5$ satisfy the system of equations below.

$2x_1+x_2+x_3+x_4+x_5=6$
$x_1+2x_2+x_3+x_4+x_5=12$
$x_1+x_2+2x_3+x_4+x_5=24$
$x_1+x_2+x_3+2x_4+x_5=48$
$x_1+x_2+x_3+x_4+2x_5=96$

Solution

Adding all five equations gives us $6(x_1 + x_2 + x_3 + x_4 + x_5) = 6(1 + 2 + 4 + 8 + 16)$ so $x_1 + x_2 + x_3 + x_4 + x_5 = 31$. Subtracting this from the fourth given equation gives $x_4 = 17$ and subtracting it from the fifth given equation gives $x_5 = 65$, so our answer is $3\cdot17 + 2\cdot65 = \boxed{181}$.

See also

1986 AIME (ProblemsAnswer KeyResources)
Preceded by
Problem 3
Followed by
Problem 5
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
All AIME Problems and Solutions

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