5th Class Mathematics Mensuration

Mensuration

• Perimeter:

The total boundary length of a closed figure is called its perimeter. It is expressed in usual units of measurement of length.

• Area:

The amount of surface enclosed by a closed figure is called its area.

(a) Area is measured in square units.

(b) 1 m = 100 cm; 1 sq. m = 10000 sq. cm;

(c) 1 cm = 10 mm; 1 sq. cm = 100 sq. mm

• Volume:

The space occupied by an object is called its volume.

(a) Volume is measured in cubic units.

(b) 1 cu m = 1000000 cu cm;

(c) 1 cu cm = 1000 cu mm

• Cube:

It is a solid figure with 6 square surfaces.

• Volume of a cube = edge x edge x edge cu units.

• Cuboid:

It is a solid figure with 6 rectangular surfaces.

• Volume of a cuboid = length × breadth × height cubic units.

V =\[l\] × b × h

\[\therefore l=\frac{\text{V}}{\text{bh}};\]       \[b=\frac{\text{V}}{l\text{h}};\]     \[\text{h}=\frac{\text{V}}{l\text{b}};\]                          

• The shape obtained on opening a solid shape is called a net.
• A net can be folded back or closed into form a solid.

• Net of a cube :

The net of a cube has 6 squares.

• Net of a cuboid :

The net of a cuboid has 6 rectangles.