Class 8 Maths – Chapter 11

Mensuration

STEP 3: NCERT Solved Examples

Example 1

Find the area of a rectangle whose length is 10 cm and breadth is 7 cm.

Solution:

Length (l) = 10 cm

Breadth (b) = 7 cm

Area of rectangle = l × b

= 10 × 7

= 70 cm²

Example 2

Find the volume of a cube whose side is 5 cm.

Solution:

Side (a) = 5 cm

Volume of cube = a³

= 5³

= 125

Volume = 125 cm³

Example 3

Find the curved surface area of a cylinder of radius 7 cm and height 10 cm.

Solution:

Radius (r) = 7 cm

Height (h) = 10 cm

CSA of cylinder = 2πrh

= 2 × (22/7) × 7 × 10

= 440

Curved Surface Area = 440 cm²

Example 4

Find the total surface area of a cube of side 4 cm.

Solution:

Side (a) = 4 cm

TSA of cube = 6a²

= 6 × 4²

= 6 × 16

= 96 cm²

📌 Exam Writing Tip

Always write Given, Formula, Substitution and Answer clearly.