If the cylinder and the cone shown the same volume, then the radius and height of the cone could be which of these? Diameter 10 and height is 4: (radius of the cone = 5, height of the cone = 12; radius of the cone = 5, height of the cone = 4; radius of the cone = 15, height of the cone = 4; radius of the cone = 15, height of the cone = 12)

1 answer

To find out which set of dimensions for the cone gives it the same volume as the cylinder, we need to use the formulas for the volume of a cylinder and a cone.

  1. Volume of a Cylinder: \[ V_{\text{cylinder}} = \pi r_{\text{cylinder}}^2 h_{\text{cylinder}} \]

  2. Volume of a Cone: \[ V_{\text{cone}} = \frac{1}{3} \pi r_{\text{cone}}^2 h_{\text{cone}} \]

Given that the diameter of the cylinder is 10, the radius \( r_{\text{cylinder}} \) is \( \frac{10}{2} = 5 \).

Let’s consider \( h_{\text{cylinder}} \) to determine the volume of the cylinder. We can compute a general expression for volume in relation to the height of the cylinder.

  1. Volume of the Cylinder (assuming height = 4): \[ V_{\text{cylinder}} = \pi (5)^2 (4) = 100\pi \]

Now, we need to check which of the cone dimensions provided would result in a cone volume of \( 100\pi \).

Options for the cone:

  1. Radius = 5, Height = 12: \[ V_{\text{cone}} = \frac{1}{3} \pi (5^2)(12) = \frac{1}{3} \pi (25)(12) = \frac{300}{3} \pi = 100\pi \]

  2. Radius = 5, Height = 4: \[ V_{\text{cone}} = \frac{1}{3} \pi (5^2)(4) = \frac{1}{3} \pi (25)(4) = \frac{100}{3} \pi \neq 100\pi \]

  3. Radius = 15, Height = 4: \[ V_{\text{cone}} = \frac{1}{3} \pi (15^2)(4) = \frac{1}{3} \pi (225)(4) = \frac{900}{3} \pi = 300\pi \neq 100\pi \]

  4. Radius = 15, Height = 12: \[ V_{\text{cone}} = \frac{1}{3} \pi (15^2)(12) = \frac{1}{3} \pi (225)(12) = \frac{2700}{3} \pi = 900\pi \neq 100\pi \]

Conclusion:

The only dimensions for the cone that equal the volume of the cylinder when the cylinder has a diameter of 10 and height of 4 is:

  • Radius = 5, Height = 12.