Question

The length of a rectangle is 2 cm more than
3 times its width. Its area is 85 cm?. Find the
dimensions of the rectangle.

Answer 1

Answer:

Width of rectangle = 5 cm

Length of rectangle =  17 cm

Step-by-step explanation:

Let the dimensions of rectangle:

Width of rectangle = x

Length of rectangle = 3x+2

Area of rectangle = 85 cm

We need to find dimensions of rectangle i.e length and width.

The formula used is: $Area\:of\:rectangle=Length\times Width$

Putting values and finding dimensions

$Area\:of\:rectangle=Length\times Width\\85=3x+2 \times x\\85=3x^2+2x\\The\;equation\:will\:be:\\3x^2+2x-85=0$

Now, finding value of x using quadratic formula:

$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$

We have, a =3, b =2 and c=-85

$x=\frac{-2\pm \sqrt{(2)^2-4(3)(-85)}}{2(3)}\\x=\frac{-2\pm \sqrt{4+1020}}{6}\\x=\frac{-2\pm \sqrt{1024}}{6}\\x=\frac{-2\pm 32}{6}\\x=\frac{-2+ 32}{6}\:or\:x=\frac{-2- 32}{6}\\x=5\:or\:x=-5.6$

So, we get x = 5 and x = -5.6

But since the width of rectangle cannot be negative so, we would consider x = 5

Now, the dimensions of rectangle will be:

Width of rectangle = x = 5 cm

Length of rectangle = 3x+2 = 3(5) + 2 = 15+2 = 17 cm