The area of a rectangular wall in a classroom is 133 ft.². Its length is 2 feet shorter than three times its width. Find the length and width of the wall of the classroom.

The area of a rectangular wall in a classroom is 133 ft Its length is 2 feet shorter than three times its width Find the length and width of the wall of the cla class=

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ANSWER

[tex]width=7ft;\text{ }length=19ft[/tex]

EXPLANATION

Let the length of the rectangle be L.

Let the width of the rectangle be W.

The length of the classroom is 2 feet shorter than three times its width. This implies that:

[tex]L=3W-2[/tex]

The area of a rectangle is given by:

[tex]A=L*W[/tex]

Hence, by substituting the given values into the equation, we have that:

[tex]\begin{gathered} A=(3W-2)*W \\ 133=3W^2-2W \\ \Rightarrow3W^2-2W-133=0 \end{gathered}[/tex]

Solve the quadratic equation above by applying the quadratic formula:

[tex]W=\frac{-b\pm\sqrt{b^2-4ac}}{2a}[/tex]

where

a = 3, b = -2, c = -133

Therefore:

[tex]\begin{gathered} W=\frac{-(-2)\pm\sqrt{(-2)^2-(4*3*-133)}}{2(3)} \\ W=\frac{2\pm\sqrt{4+1596}}{6}=\frac{2\pm\sqrt{1600}}{6} \\ W=\frac{2\pm40}{6} \\ W=\frac{2+40}{6};\text{ }W=\frac{2-40}{6} \\ W=\frac{42}{6};\text{ }W=\frac{-38}{6} \\ W=7;\text{ }W=-\frac{19}{3} \end{gathered}[/tex]

Since the width of a rectangle cannot be negative, the width of the rectangle is:

[tex]W=7\text{ }ft[/tex]

To find the length of the rectangle, substitute the value of W into the equation for L:

[tex]\begin{gathered} L=3(7)-2=21-2 \\ L=19\text{ }ft \end{gathered}[/tex]

Hence, the width of the rectangle is 7 ft and its length is 19 ft.