Mensuration (NCERT Ch. 11)

• Find the area of a trapezium, rhombus, and general quadrilateral.
• Find the surface area and volume of a cube, cuboid, and cylinder.

1. Area of a trapezium = (1/2) x (sum of parallel sides) x height.
2. Area of a rhombus = (1/2) x product of diagonals.
3. Surface area of a cube = 6 x side²; volume of a cube = side³.
4. Surface area of a cuboid = 2(lb + bh + hl); volume of a cuboid = l x b x h.
5. Volume of a cylinder = π x r² x h; curved surface area = 2πrh.

Find the volume of a cuboid with length 5 cm, breadth 4 cm, height 3 cm.

Volume = l x b x h = 5 x 4 x 3 = 60 cubic cm

• Using the wrong formula for trapezium area (forgetting the 1/2 factor or using only one parallel side).
• Confusing surface area (total covering, sq units) with volume (space occupied, cubic units).
• Mixing up radius and diameter in cylinder formulas.

• Find the area of a rhombus with diagonals 10 cm and 8 cm.
• Find the surface area of a cube with side 4 cm.

Open the Practice tab for graded questions on Mensuration (NCERT Ch. 11).