ICSE Class 8 Maths, Unit 5: Mensuration

What this unit aims at

Children should be clear about the idea of area as measure of region occupied by a shape on a surface and the formulae to find area of rectangle and square. In this class the theme will enable them to evolve the methods of finding the area of shapes like trapezium and other polygons. The idea behind the formulae of finding area of rectilinear shapes is moving from known to unknown i.e. developing the methods using the formulae they know like rectangle. Children will develop the ability to think how a trapezium and parallelogram can be converted into a rectangle of same area. Using this understanding the methods of finding the surface area of 3-D figures is to be introduced. For this the nets of simple figures like cuboid will be useful to visualize the shapes of different surfaces of this figure. This visualization will help children in evolving formula for finding area of all surfaces.

Your child should be able to

• find area of trapezium and polygons by using square grid and also by using formulae
• find surface area of cuboid, cube and cylinder through their nets and later on by using formulae
• form formula to find volume of a cuboid and cylinder by observing and generalizing patterns of counting units cubes that completely fill the cuboids. find volume and capacity (measurement of capacity) of cuboidal and cylindrical vessels

Key concepts in this unit

• Area of a trapezium, a polygon and semi-circle.
• Surface area of a cube, cuboid, cylinder.
• Idea of Total surface area and curved surface areas of various 3-D figures
• Concept of volume, measurement of volume using a basic unit, volume of a cube, cuboid and cylinder
• Volume and capacity (measurement of capacity)