8 cm

15 cm

If the cylinder were dilated using a scale factor of 4, what would be the new surface area? The formula for the surface area of a cylinder is SA = 2πrh + 2πr^2.

a. 23π cm^2
b. 1,472π cm^2
c. 368π cm^2
d. 5,888π cm^2

1 answer

To find the new surface area of the cylinder after dilating it by a scale factor of 4, we first need to calculate the original surface area using the given dimensions.

The formula for the surface area (SA) of a cylinder is:

\[ SA = 2\pi rh + 2\pi r^2 \]

Given:

  • radius \( r = 8 , \text{cm} \)
  • height \( h = 15 , \text{cm} \)

Step 1: Calculate the original surface area.

First, we substitute the values into the formula:

  1. Calculate the lateral surface area \( 2\pi rh \):

\[ 2\pi rh = 2\pi (8)(15) = 240\pi , \text{cm}^2 \]

  1. Calculate the area of the top and bottom \( 2\pi r^2 \):

\[ 2\pi r^2 = 2\pi (8^2) = 2\pi (64) = 128\pi , \text{cm}^2 \]

  1. Combine them to find the total surface area:

\[ SA = 240\pi + 128\pi = 368\pi , \text{cm}^2 \]

Step 2: Determine the new dimensions after dilation.

When the cylinder is dilated using a scale factor of 4, the new dimensions will be:

  • New radius \( r' = 4 \times r = 4 \times 8 , \text{cm} = 32 , \text{cm} \)
  • New height \( h' = 4 \times h = 4 \times 15 , \text{cm} = 60 , \text{cm} \)

Step 3: Calculate the new surface area.

Now we use the new dimensions into the surface area formula:

  1. Calculate the new lateral surface area:

\[ 2\pi r'h' = 2\pi (32)(60) = 3840\pi , \text{cm}^2 \]

  1. Calculate the area of the top and bottom with the new radius:

\[ 2\pi (r')^2 = 2\pi (32^2) = 2\pi (1024) = 2048\pi , \text{cm}^2 \]

  1. Combine to find the total surface area:

\[ SA' = 3840\pi + 2048\pi = 5888\pi , \text{cm}^2 \]

Thus, the new surface area of the cylinder after dilation is:

\[ \boxed{5,888\pi , \text{cm}^2} \]

Therefore, the answer is (d) \( 5,888\pi , \text{cm}^2 \).