Surface area of a sphere is given by [tex]4 \pi r^2[/tex], where [tex]r[/tex] is the radius.

The sphere below has a radius of 7 cm. Work out the surface area of the sphere. Give your answer in terms of [tex]\pi[/tex] and remember to give the correct units.



Answer :

To find the surface area of the sphere with a radius of 7 cm, we can use the surface area formula for a sphere given by

[tex]\[ \text{Surface Area} = 4\pi r^2 \][/tex]

where [tex]\( r \)[/tex] is the radius of the sphere.

1. Identify the radius: We are given that the radius [tex]\( r \)[/tex] is 7 cm.

2. Plug the radius into the formula:
[tex]\[ \text{Surface Area} = 4\pi (7)^2 \][/tex]

3. Calculate the squared radius:
[tex]\[ (7)^2 = 49 \][/tex]

4. Multiply by 4:
[tex]\[ 4 \cdot 49 = 196 \][/tex]

5. Multiply by [tex]\(\pi\)[/tex] to express the answer in terms of [tex]\(\pi\)[/tex]:
[tex]\[ 196 \pi \][/tex]

So, the surface area of the sphere is [tex]\( 196\pi \, \text{cm}^2 \)[/tex].

Now, also note that often we calculate the numerical value using [tex]\(\pi \approx 3.14159\)[/tex].

6. Calculate the numerical value:
[tex]\[ 196 \pi \approx 196 \times 3.14159 \approx 615.752 \][/tex]

This matches the previously noted result of approximately 615.752.

Therefore, the surface area of the sphere, in terms of [tex]\(\pi\)[/tex], is [tex]\(196\pi \, \text{cm}^2\)[/tex], and numerically it is approximately [tex]\(615.752 \, \text{cm}^2\)[/tex].