A circle is a closed figure that can be drawn using a constant length from a fixed-point center. A sphere is a three-dimensional circle. Circle and sphere both are round and measured using radius. Here we are going to calculate the surface area, the volume of a sphere by different sphere formula.

**Sphere Formula**

**What is the Sphere?**

A sphere is a three-dimensional counterpart of a circle, with all its points lying in space at a constantÂ distance from the fixed point or the center, called the radius of the sphere. Radius of the sphere denoted as r.

**The diameter of a sphere:** The line passing through the center from one end to the other called the diameter of the sphere. The diameter of the sphere denoted as D.

Diameter = 2 times radius of the sphere

D = 2Â Ã— r

**Circumference of a sphere:** Circumference of a sphere is the distance covered around the sphere. The unit of the circumference is the same as the radius.

Circumference = \(2 \times \pi \times r\)

**The surface area of a sphere:**Â The surface area of a sphere is the number of square units that will exactly cover the surface of a sphere. The unit of the surface area of sphere is a square unit mÂ²

The surface area of a sphere is

Surface Area of sphere = 4 times the area of a circle

Surface Area of sphere =\(4 \times \pi \times r^{2}\)

Where

Â r | the radius of the sphere |

**The volume of a sphere:** Volume of sphere is the number of cubic units that fill a sphere. The unit of volume of the sphere is a cubic unit mÂ³

The volume enclosed by a sphere is

Volume of sphere = \(\frac{4}{3}\)Ï€ rÂ³

Where,

Â r | the radius of the sphere |

**The volume of spherical shell: **AÂ spherical shellÂ is a region between two concentric spheres having different radii.

Volume of a spherical shell = \(\frac{4}{3}\pi R^{3} – \frac{4}{3}\pi r^{3}\)

V =\(\frac{4}{3}\pi (R^{3}-r^{3})\)

Where,

R | The outer radius of the sphere |

r | The inner radius of the sphere |

**Solved Examples **

Q 1:Â The radius of the sphere is 5 cm. Find the diameter, circumference, surface area and volume of a sphere?

Solution: Given, r = 5 cm

Diameter of a sphere = 2Â Ã— r

= 2Â Ã— 5

=10 cm

Circumference of a sphere = \(2\times \pi \times r\)

= \(2\times \pi \times 5\)

= 31.41 cm

Surface Area of sphere =\(4 \times \pi \times r^{2}\)

= \(4 \times \pi \times 5^{2}\)

= \(4 \times \times 3.14 Â \times 25\)

= 314.16 cmÂ²

Volume of a sphere** = \(**\frac{4}{3}\pi r^{3}\)

= \(\frac{4}{3}\pi 5^{3}\)

= \(\frac{4}{3} \times 3.14 \times 125\)

= 523.60 cmÂ³

Q 2: A shopkeeper has one ladoo of radius 10 cm. With the same material used to form a big ladoo, how many ladoos of radius 5 cm can be made.

Solution: Let the number of smaller ladoos that can be made from a bigger ladoo beÂ *x*.

Here,

The radius of the bigger ladoo (R) = 10 cm

The radius of the smaller ladoo (r) = 5 cm

So, the volume of the big ladoo is equal to the volume ofÂ xÂ small ladoos.

Volume of the big ladoo = Volume of the x small ladoos

\(\frac{4}{3}\pi R^{3}\) = \(\frac{4}{3}\pi r^{3}\)

\(\frac{4}{3}\pi 10^{3}\) = \(x\frac{4}{3}\pi 5^{3}\)

\(10^{3} = x 5^{3}\)

x = \(\frac{10^{3}}{5^{3}}\)

x = \(\frac{1000}{125}\)

x = 8

Therefore, 8 ladoos of 5 cm can be made from one big ladoo of radius 10 cm.

I get a different answer for first example.

I got Q1 as 20.5

median 23 and

Q3 26