Question

The length of a rectangle is 4 cm less than it’s width. If the area of the rectangle is 165 cm^2. What are the dimensions of the rectangle?

Answer 1

Answer:

The dimensions are 11 cm by 15 cm

Step-by-step explanation:

Area of a rectangle = (length)(width).

Let L represent the length and W the width.

Since L = W - 4, we have

Area of rectangle = (W - 4)W = 165 cm^2.

Thus, w^2 - 4W - 165 = 0.  We can solve for W using the quadratic formula:

a = 1, b = -4 and c = -165.  Thus,

        -(-4) ± √ [ (-4)² - 4(1)(-165) ]

W = ---------------------------------------

                        2

         4 ± √ [16 + 660 ]

W = ------------------------------

                       2

         4 ± √ [ 676 ]                    4 ± 26

W = -----------------------  =   W = -------------  =  W  = 2 ± 13

                  2                                  2

Thus, W is 2 + 13 = 15.  It cannot be negative, so we discard 2 - 13 = -11.

If the width, W, is 15, then the length is 4 less, or L = 11.

The dimensions are 11 cm by 15 cm