CPM Homework Help : GC Problem 1-25

Read the Math Notes box for this lesson, which describes how to find the area and perimeter of a shape. Then examine the rectangle at right. If the perimeter of this shape is $120$ cm, which equation below represents this fact? Once you have selected the appropriate equation, solve for $x$ .

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interior rectangle

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right edge $2x+5$

bottom edge $6x-1$

$2x+5+6x-1=120$

$4(6x-1)=120$

$2(6x-1)+2(2x+5)=120$

$(2x+5)(6x-1)=120$

Answer:

The equation for the perimeter is part (c).

$\begin{array}{r} 2(6x-1)+2(2x+5)=120\\ (12x-2)+(4x+10)=120\\ 16x+8=120 \\ 16x=112 \\ x=7 \quad \end{array}$