Adrian is painting the outside of a cylinder that he plans to use as a coffee table. The cylinder has a radius of 4 feet and a height of 3 feet.

Adrian wants to paint all around the outside of the cylinder, including the top and bottom faces.

In order to understand how much paint is needed, he wants to know the surface area of the outside of the cylinder. What is the surface area of the cylinder, rounded to two decimal places? use pi instead of 3.14

2 answers

To calculate the surface area of a cylinder, we need to determine both the lateral surface area and the area of the top and bottom faces.

  1. Lateral Surface Area: The lateral surface area \(A_{lateral}\) of a cylinder is given by the formula: \[ A_{lateral} = 2\pi rh \] where \(r\) is the radius and \(h\) is the height.

  2. Area of the Top and Bottom Faces: The area of one circular face is given by the formula: \[ A_{circle} = \pi r^2 \] Since there are two circular faces (top and bottom), the total area of the faces is: \[ A_{faces} = 2\pi r^2 \]

  3. Total Surface Area: The total surface area \(A_{total}\) of the cylinder is the sum of the lateral surface area and the area of the two faces: \[ A_{total} = A_{lateral} + A_{faces} \]

Now, substituting the given values \(r = 4\) feet and \(h = 3\) feet into the formulas:

Lateral Surface Area: \[ A_{lateral} = 2\pi rh = 2\pi(4)(3) = 24\pi \]

Area of the Top and Bottom Faces: \[ A_{faces} = 2\pi r^2 = 2\pi(4^2) = 2\pi(16) = 32\pi \]

Total Surface Area: \[ A_{total} = A_{lateral} + A_{faces} = 24\pi + 32\pi = 56\pi \]

To find the total surface area in numeric form, we can substitute \(\pi\) (approximately 3.14) if needed: \[ A_{total} \approx 56 \times 3.14 \approx 175.84 \]

Rounded to two decimal places, the total surface area of the cylinder is: \[ \boxed{175.84 \text{ square feet}} \]

However, if we need to provide the answer in terms of \(\pi\), the surface area remains: \[ A_{total} = 56\pi \text{ square feet} \]

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