NCERT Solutions for Class 9 Maths Exercise 13.4 Surface Areas and Volumes in Hindi and English Medium updated for CBSE Session 2022-2023. Class 9 Maths Exercise 13.4 deals with the surface area of Sphere and hemi-sphere. All the questions are solved step by step using suitable formulae. Download PDF and video format of solutions to understand better.

## NCERT Solutions for Class 9 Maths Exercise 13.4

### Sphere and its Parts

As we have mentioned above a sphere is a 3-dimensional solid figure, this is made of all points in the space which lie at the equidistance known as Radius (r). This origin fixed point is called the Center of the sphere.

Once you have the radius, the formulae are usually pretty straightforward to remember. Just as with the circumference of the circle, you will need to use π values. Basically, you can round this infinite number to 3.14 or 22/7.

#### Formulae for Surface Areas of Sphere

As per stated information you will get the following formulae for Curved Surface Area or Total Surface Area as 4 π r2. The figure 18, shown in NCERT Maths books, is sphere. When we will cut it in half, get two equal parts of the sphere that is known hemisphere.

Similar to the above given formulae there are shall be four formulae that are related to the Sphere. You have to remember the Surface area of a sphere, the surface area of the hemisphere, curved surface area, and total surface area of hemisphere.

##### Solving process of Exercise 13.4 in Class 9 Maths

Most of the questions of Class 9 Maths Exercise 13.4 are based on direct formula. The best part of the formulae is that you can derive it to which will help you to remember for a longer time.

It is absolutely necessary to remember these formulae. This could be a little difficult to remember but it is the best way for solving surface area and volume. You can make your surface area concepts to learn and demonstrate to your friends how the concept actually works.

###### Surface areas in day to day life

For instance – use different shape containers such as bread, biscuits, and butter. Cut some of the edges so that they stay together, but can be unfolded to show how different surfaces make the shape and what measurements are.

These practical activities and manipulative are so effective that they shall help you then imagine the function of the shapes and surfaces. In exercise 13.4 all the 9 questions are easy to solve. Most of the questions ask you to calculate the spheres-related areas.