A rectangle measures 12m by 5m a path of constant width runs along one side and one end. If the total area of the plot and the path is 120m² find the width of the path

1 answer

Let the width of the path be \( w \) meters.

The original rectangle has dimensions:

  • Length = 12 m
  • Width = 5 m

The area of the original rectangle is: \[ A_{\text{rectangle}} = 12 \times 5 = 60 , \text{m}^2 \]

When the path of width \( w \) is added to one side and one end of the rectangle, the new dimensions become:

  • New length = \( 12 + w \)
  • New width = \( 5 + w \)

The area of the plot including the path is: \[ A_{\text{total}} = (12 + w)(5 + w) \]

We know the total area of the plot and the path is 120 m², so we can set up the equation: \[ (12 + w)(5 + w) = 120 \]

Expanding the left side: \[ 12 \times 5 + 12w + 5w + w^2 = 120 \] \[ 60 + 17w + w^2 = 120 \]

Rearranging gives us: \[ w^2 + 17w + 60 - 120 = 0 \] \[ w^2 + 17w - 60 = 0 \]

Now we can solve this quadratic equation using the quadratic formula: \[ w = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] where \( a = 1 \), \( b = 17 \), and \( c = -60 \).

Calculating the discriminant: \[ b^2 - 4ac = 17^2 - 4 \times 1 \times (-60) = 289 + 240 = 529 \]

Taking the square root: \[ \sqrt{529} = 23 \]

Now substituting into the quadratic formula: \[ w = \frac{-17 \pm 23}{2} \]

Calculating the two possible solutions: 1. \[ w = \frac{-17 + 23}{2} = \frac{6}{2} = 3 \] 2. \[ w = \frac{-17 - 23}{2} = \frac{-40}{2} = -20 \]

Since a width cannot be negative, we take the positive solution: \[ w = 3 \]

Thus, the width of the path is: \[ \boxed{3 , \text{m}} \]