Difference between revisions of "2002 AMC 10P Problems/Problem 6"

(Solution 1)
(Solution 1)
 
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== Solution 1==
 
== Solution 1==
Let <math>l</math> be the length of the rectangle and <math>w</math> be the width of the rectangle. We are given <math>2l+2w=100</math> and <math>l^2+w^2=x^2.</math> We are asked to find <math>lw.</math> Using a bit of algebraic manipulation:
+
Let <math>l</math> be the length of the rectangle and <math>w</math> be the width of the rectangle. We are given <math>2l+2w=100</math> and <math>l^2+w^2=x^2.</math> We are asked to find the area, which is equivalent to <math>lw.</math> Using a bit of algebraic manipulation:
 
<cmath>\begin{align*}
 
<cmath>\begin{align*}
2l+2w=100 \\
+
2l+2w &= 100 \\
l+w=50 \\
+
l+w &= 50 \\
(l+w)^2=2500 \\
+
(l+w)^2 &= 2500 \\
l^2 + w^2 +2lw = 2500 \\
+
l^2 + w^2 +2lw &= 2500 \\
x^2 + 2lw = 2500 \\
+
x^2 + 2lw &= 2500 \\
lw=\frac{2500-x^2}{2} \\
+
lw &= \frac{2500-x^2}{2} \\
lw=1250 - \frac{x^2}{2} \\
+
lw &= 1250 - \frac{x^2}{2} \\
 
\end{align*}</cmath>
 
\end{align*}</cmath>
  

Latest revision as of 21:04, 14 July 2024

Problem

The perimeter of a rectangle $100$ and its diagonal has length $x.$ What is the area of this rectangle? $\text{(A) }625-x^2 \qquad \text{(B) }625-\frac{x^2}{2} \qquad \text{(C) }1250-x^2 \qquad \text{(D) }1250-\frac{x^2}{2} \qquad \text{(E) }2500-\frac{x^2}{2}$

Solution 1

Let $l$ be the length of the rectangle and $w$ be the width of the rectangle. We are given $2l+2w=100$ and $l^2+w^2=x^2.$ We are asked to find the area, which is equivalent to $lw.$ Using a bit of algebraic manipulation: \begin{align*} 2l+2w &= 100 \\ l+w &= 50 \\ (l+w)^2 &= 2500 \\ l^2 + w^2 +2lw &= 2500 \\ x^2 + 2lw &= 2500 \\ lw &= \frac{2500-x^2}{2} \\ lw &= 1250 - \frac{x^2}{2} \\ \end{align*}

Thus, our answer is $\boxed{\textbf{(D) } 1250 - \frac{x^2}{2}}.$

See also

2002 AMC 10P (ProblemsAnswer KeyResources)
Preceded by
Problem 5
Followed by
Problem 7
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

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