# RD Sharma Class 9 Chapter 18 Solutions (Surface Area and Volume of a Cuboid and Cube)

RD Sharma Solutions for Class 9 Chapter 18 is prepared to enable you to study about the solid three-dimensional figures like cuboid and cube. They are just not any plain figures which can be drawn by hands. You will also learn to find the surface areas and volumes of cuboid and cube.

The chapter of RD Sharma Class 9 Maths Solutions consists of two exercises with 47 small and long questions. Addition to that, you will come across with 22 multiple questions. It just consists of two solid shapes. That is cuboid and cube. You will come across the total surface area of cuboid and cube, the lateral surface area of cuboid and cube, diagonals of cuboid and cube and length of all edges of cuboid and cube. The chapter gains its significance when at the latter part volume of a cuboid and cube is introduced. You will see some formulas to solve the questions. By learning that only, you can gain access to get a thorough understanding of finding answers.

Instasolv is here to help you learn all those shapes, its complexities and its importance. With our help, you can easily understand the chapter clearly. A fine explanation of all the terms is available with us for your betterment.

## Topics covered in RD Sharma Solutions for Class 9 Chapter 18

**Units of measurement of area and volume**

Some units of measurement of areas are

1 *cm ^{2}* = 100

*mm*

^{2}1 *d**m ^{2}* = 100

*cm*

^{2}1 *hm ^{2}* = 100 dm2

1 *k**m ^{2}* = 100 hectare

Some units of measurement of volumes are

1 *cm ^{3}* = 1000

*mm*

^{3}1 *m ^{3}* = 1 kilolitre

**Cuboid**

A solid figure bounded by six rectangular plane regions is termed as a cuboid. For example, objects like matchbox, book, any box represents cuboid. The six plane regions are called six faces of cuboid. The top and bottom face are opposite faces of cuboid and any other face apart from that is called an adjacent face.

When any adjacent faces of cuboid meet in a line segment, we call it an edge of a cuboid.

When two edges meet, there is a third edge which meets at the same endpoint as well. That intersecting point of three edges is called a vertex of a cuboid. So, cuboids generally have eight vertices.

Any face of the cuboid can be termed as a base of a cuboid. At base, where four faces meet are called lateral of the cuboid.

**The surface area of a cuboid**

The total surface area of a cuboid is the sum of the areas of its six faces.

The formula of surface area of cuboid = 2(length*breadth + breadth*height + height*length) cm^{2}

When we leave the top and bottom faces of cuboids while calculating, we get the lateral surface of a cuboid.

The formula of the lateral surface area of a cuboid = 2(length + breadth) height

**The volume of a cuboid**

When any object is filled with air or liquid, it’s called the capacity of the object. That capacity of an object is known as the volume of the substance.

Therefore, volume of the cuboid= length*breadth*height

Also, the volume of the cuboid= Area of the base*height

**Cube**

When a cuboid has its length, breadth and height all equal, it is called a cube.

Each edge of a cube is termed as a side of a cube.

**The surface area of a cube**

Since, the Cube has all the faces of similar sides, Surface area of a cube is the sum of areas of six faces.

The Formula of the surface area of cube= 6(edge) square.

The Lateral surface area of cube= 4 (edge) square.

**The volume of a cube**

Similar to a cuboid, any cube which is filled with some space or liquid, it is the volume of a cube.

As cube has it’s all sides equal, the formula of volume of a cube= length*length*length

### Discussions of RD Sharma Solutions for Class 9 Chapter 18

- In the first exercise, there are questions about the lateral and total surface area of cuboid and cube. You will have to find the ratio. Some questions are about finding the percentage of surface areas, finding dimensions, height, length and breadth of the room. Following some assumptions, you will also see a few word problems.
- The second exercise is about finding the volume of a cube and cuboid. Questions to find out dimensions, volume, surface area and diagonal are also asked. Moreover, few questions are asked to prove the statement. The exercise has a lot of word problems.

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