Difference between revisions of "2011 AMC 10A Problems/Problem 9"

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A rectangular region is bounded by the graphs of the equations y=a, y=-b, x=-c, and x=d, where a,b,c, and d are all positive numbers. Which of the following represents the area of this region?  
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== Problem 9 ==
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A rectangular region is bounded by the graphs of the equations <math>y=a, y=-b, x=-c,</math> and <math>x=d</math>, where <math>a,b,c,</math> and <math>d</math> are all positive numbers. Which of the following represents the area of this region?
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<math> \textbf{(A)}\ ac+ad+bc+bd\qquad\textbf{(B)}\ ac-ad+bc-bd\qquad\textbf{(C)}\ ac+ad-bc-bd  \quad\quad\qquad\textbf{(D)}\ -ac-ad+bc+bd\qquad\textbf{(E)}\ ac-ad-bc+bd </math>
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== Solution ==
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We have a rectangle of side lengths <math>(a - -b)</math> and <math>(d - -c)</math> Thus the area of this rectangle is <math>(a + b)(c + d) = ac + ad + bc + bd</math>
 
We have a rectangle of side lengths <math>(a - -b)</math> and <math>(d - -c)</math> Thus the area of this rectangle is <math>(a + b)(c + d) = ac + ad + bc + bd</math>
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== See Also ==
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{{AMC10 box|year=2011|ab=A|num-b=8|num-a=10}}

Revision as of 10:53, 8 May 2011

Problem 9

A rectangular region is bounded by the graphs of the equations $y=a, y=-b, x=-c,$ and $x=d$, where $a,b,c,$ and $d$ are all positive numbers. Which of the following represents the area of this region?

$\textbf{(A)}\ ac+ad+bc+bd\qquad\textbf{(B)}\ ac-ad+bc-bd\qquad\textbf{(C)}\ ac+ad-bc-bd   \quad\quad\qquad\textbf{(D)}\ -ac-ad+bc+bd\qquad\textbf{(E)}\ ac-ad-bc+bd$

Solution

We have a rectangle of side lengths $(a - -b)$ and $(d - -c)$ Thus the area of this rectangle is $(a + b)(c + d) = ac + ad + bc + bd$

See Also

2011 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 8
Followed by
Problem 10
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 AMC 10 Problems and Solutions