Use the image to answer the question.

A hemisphere is placed on top of an inverted cone. The back of the circumference, the radius, and the perpendicular height of the cone are marked with dashed lines. The radius and the height make a right angle and are perpendicular.

An engineer wants to know the volume of the following object composed of a hemisphere and a cone. She knows the height of the cone is equal to the diameter of the hemisphere, and the volume of the cone is 12 m^3
. What is the volume of the whole object?(1 point)
Responses

36 m3
36 m cubed

18 m3
18 m cubed

24 m3
24 m cubed

There is not enough information to say.

1 answer

To find the volume of the entire object composed of a hemisphere and a cone, we can first calculate the volume of the hemisphere and then add it to the volume of the cone.

  1. Volume of the cone: Given as 12 m³.

  2. Height of the cone (h) is equal to the diameter of the hemisphere (D), which means \( h = 2r \), where \( r \) is the radius of the hemisphere.

  3. Volume of the hemisphere: The formula for the volume of a hemisphere is given by:

    \[ V = \frac{2}{3} \pi r^3 \]

  4. To find the radius \( r \) of the hemisphere, we also need to relate it to the volume of the cone: The volume of a cone is given by:

    \[ V = \frac{1}{3} \pi r^2 h \]

    Since \( h = 2r \), we can substitute \( h \) into the cone volume formula:

    \[ V_{\text{cone}} = \frac{1}{3} \pi r^2 (2r) = \frac{2}{3} \pi r^3 \]

  5. Setting this equal to the given volume of the cone:

    \[ \frac{2}{3} \pi r^3 = 12 \]

  6. Solving for \( r^3 \):

    \[ r^3 = 12 \cdot \frac{3}{2 \pi} = \frac{36}{2\pi} = \frac{18}{\pi} \]

  7. Now, we can find the volume of the hemisphere using its radius \( r \):

    \[ V_{\text{hemisphere}} = \frac{2}{3} \pi r^3 = \frac{2}{3} \pi \left( \frac{18}{\pi} \right) = \frac{36}{3} = 12 , \text{m}^3 \]

  8. Finally, we add the volumes of the cone and hemisphere:

    \[ V_{\text{total}} = V_{\text{cone}} + V_{\text{hemisphere}} = 12 + 12 = 24 , \text{m}^3 \]

Thus, the volume of the whole object is 24 m³. Therefore, the correct response is:

24 m3 or 24 m cubed.