Class 6 · Chapter 10

Mensuration

Perimeter and area of simple plane figures (rectangle, square, triangle).

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Tip: open the NCERT PDF for the original chapter text alongside the notes here.

Detailed theory

Perimeter = total distance around the boundary. Rectangle:

2(l+b)

. Square:

4a

. Triangle: sum of three sides. Circle's perimeter is called the circumference.

Key concepts & formulas

Perimeter of a rectangle

= 2(l + b)

Area of a rectangle

= l \times b

Perimeter of a square

= 4a

; area

= a^2

Perimeter of a triangle

=

sum of three sides.

Area of a right triangle

= \tfrac{1}{2} \times \text{base} \times \text{height}