A circular shaped ball with a diameter or radius is called a sphere.A diameter which is a straight line through the center of a sphere and with the end points on the boundary is called its diameter.

The section of the sphere by the plane is called a hemisphere. Let’s see how to find the area of Hemisphere.

## Formula of Surface area of Hemisphere.

Total Surface area of Sphere (TSA) = 4πr |

Curved Surface area of Hemisphere(CSA) = 2πr |

Total Surface area (TSA) = 3πr |

## Surface area of Hemisphere Formula Examples

**Question**: The radius of a red balloon increases from 6cm to 12 cm when the air is pumped into it. Calculate the ratios of the surface areas of the balloon in both the cases.

**Solution**:

First the radius of the balloon = 6 cm

Second the radius of the balloon = 12 cm

Surface Area of a hemisphere = 3*pi*radius ^2

The ratio of the surface areas will be

= 3*pi*(6)^{2} : 3*pi*(12)^{2}

= 6^{2} : 12^{2}

= 36 : 144

= 1 :4