The surface area of a sphere is 7.84π ft.2

What is the radius of this sphere?(1 point)
ft

7 answers

To find the radius of a sphere given its surface area, we can use the formula for the surface area of a sphere:

\[ SA = 4\pi r^2 \]

where \(SA\) is the surface area and \(r\) is the radius.

Given that the surface area \(SA\) is \(7.84\pi\) ft², we can set up the equation:

\[ 4\pi r^2 = 7.84\pi \]

Now, we can divide both sides by \(\pi\):

\[ 4r^2 = 7.84 \]

Next, divide both sides by 4:

\[ r^2 = \frac{7.84}{4} = 1.96 \]

Now, take the square root of both sides to find \(r\):

\[ r = \sqrt{1.96} \]

Calculating the square root:

\[ r = 1.4 , \text{ft} \]

Thus, the radius of the sphere is \(1.4\) ft.

How much ice cream is in a spherical scoop of ice cream with a radius of 3 cm? Use 3.14 as an approximation for pi. Round your answer to the nearest whole number.(1 point)
cm3

To find the volume of a spherical scoop of ice cream with a radius of 3 cm, we can use the formula for the volume of a sphere:

\[ V = \frac{4}{3} \pi r^3 \]

Where \( V \) is the volume and \( r \) is the radius.

Given that the radius \( r = 3 \) cm and using \( \pi \approx 3.14 \), we can substitute these values into the formula:

\[ V = \frac{4}{3} \times 3.14 \times (3)^3 \]

Calculate \( (3)^3 \):

\[ 3^3 = 27 \]

Now plug this value into the volume formula:

\[ V = \frac{4}{3} \times 3.14 \times 27 \]

Next, calculate \( \frac{4}{3} \times 27 \):

\[ \frac{4 \times 27}{3} = \frac{108}{3} = 36 \]

Now substitute this back into the volume formula:

\[ V = 36 \times 3.14 \]

Now, calculate \( 36 \times 3.14 \):

\[ V = 113.04 , \text{cm}^3 \]

Rounding to the nearest whole number, we get:

\[ V \approx 113 , \text{cm}^3 \]

Therefore, the volume of the spherical scoop of ice cream is approximately 113 cm³.

Suppose a sphere, cylinder, and cone all share the same radius and the cylinder and cone also share the same height, which is twice the radius. Which of the following is true about the relationship between the volume formulas for the sphere, cylinder, and cone?(1 point)
Responses

sphere - cone = cylinder
sphere - cone = cylinder

sphere = cylinder + cone
sphere = cylinder + cone

1 cylinder = 2 cones + 1 sphere
1 cylinder = 2 cones + 1 sphere

3 cones = 1 cylinder

Let's analyze the volumes of the sphere, cylinder, and cone based on the given dimensions:

  1. Sphere: The volume \( V_s \) of a sphere with radius \( r \) is given by:

    \[ V_s = \frac{4}{3} \pi r^3 \]

  2. Cylinder: The volume \( V_c \) of a cylinder with radius \( r \) and height \( h \) is given by:

    \[ V_c = \pi r^2 h \]

    Since the height \( h \) is twice the radius, we have \( h = 2r \). Thus, the volume of the cylinder becomes:

    \[ V_c = \pi r^2 (2r) = 2\pi r^3 \]

  3. Cone: The volume \( V_{cone} \) of a cone with radius \( r \) and height \( h \) is given by:

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

    Again, using \( h = 2r \), we have:

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

Now we can compare the volumes of the three shapes:

  • Cylinder ( \( V_c \) ): \[ V_c = 2\pi r^3 \]

  • Cone ( \( V_{cone} \) ): \[ V_{cone} = \frac{2}{3} \pi r^3 \]

  • Sphere ( \( V_s \) ): \[ V_s = \frac{4}{3} \pi r^3 \]

Now let's express these in terms of a common volume unit, \( \pi r^3 \):

  • Volume of the sphere: \[ V_s = \frac{4}{3} \pi r^3 \]

  • Volume of the cylinder: \[ V_c = 2\pi r^3 \]

  • Volume of the cone: \[ V_{cone} = \frac{2}{3} \pi r^3 \]

Now let's see if we can relate these volumes:

Comparing the volumes, we can express the cylinder's volume in terms of the cone's volume:

\[ V_c = 2 \times \text{(Volume of the cone)} = 2 \times \frac{2}{3} \pi r^3 = \frac{4}{3} \pi r^3 \]

Thus, the cylinder has the same volume as the sphere \( V_s \):

So, we have:

\[ V_s = V_c \]

Then, if we sum the cone's volume twice, we can express it as the cylinder:

\[ V_c = 2 \times V_{cone} \]

Finally, using these relationships, we find:

\[ \text{Sphere} = \text{Cylinder} + \text{Cone} \] Rearranging gives:

\[ \text{Sphere} - \text{Cone} = \text{Cylinder} \]

Therefore, the correct response is:

sphere - cone = cylinder.

The volume of a sphere is 48 m3
. What is the volume of a cylinder if its radius is the same as the sphere’s and its height is equal to the sphere’s diameter?(1 point)
m3

To determine the volume of the cylinder whose radius is the same as the sphere's and whose height is equal to the sphere's diameter, we can follow these steps:

  1. Find the radius of the sphere: The volume \( V \) of a sphere is given by the formula:

    \[ V = \frac{4}{3} \pi r^3 \]

    Given that the volume of the sphere is \( 48 , \text{m}^3 \), we can set up the equation:

    \[ \frac{4}{3} \pi r^3 = 48 \]

    To solve for \( r^3 \), first isolate the term by multiplying both sides by \( \frac{3}{4\pi} \):

    \[ r^3 = \frac{48 \times 3}{4\pi} \]

    \[ r^3 = \frac{144}{4\pi} \]

    \[ r^3 = \frac{36}{\pi} \]

    Now we can take the cube root of both sides to find \( r \):

    \[ r = \sqrt[3]{\frac{36}{\pi}} \]

    Since we don’t need to compute \( r \) exactly just yet, let’s proceed to calculate the cylinder's volume.

  2. Find the height of the cylinder: The height \( h \) of the cylinder is equal to the diameter of the sphere, which is:

    \[ h = 2r \]

  3. Find the volume of the cylinder: The volume \( V_c \) of the cylinder is given by the formula:

    \[ V_c = \pi r^2 h \]

    Substituting \( h = 2r \):

    \[ V_c = \pi r^2 (2r) = 2\pi r^3 \]

    Now, substitute \( r^3 = \frac{36}{\pi} \) into the volume formula:

    \[ V_c = 2\pi \left( \frac{36}{\pi} \right) \]

    Now simplify:

    \[ V_c = 2 \times 36 = 72 , \text{m}^3 \]

Therefore, the volume of the cylinder is 72 m³.