Question

Find the areas of the following figures in which all the corners are right-angled and the dimensions are shown
in centimetres.
5
5
12
(b)
6
(c)
9
6
5
12
20
20
20
18
6
20​

Answer 1

Answer:

1. Triangles as parts of rectangles

2. Generalising for other congruent parts of rectangles

Before moving onto exercise 11.2, the topics Area of triangle and parallelogram are discussed.

Area of a square = side × side

Area of a rectangle = length × breadth

Area of a parallelogram = base × height

Area of a triangle =1/2 × base × height

In the other half of the chapter, circles are explained. The topic is explained in two parts:

1. Circumference of Circle

The distance around a circular region is known as its circumference.

Circumference of a circle = πd

2. Area of circle

Area of circle is given by πr2

The last part of the chapter is about the conversion of units and application of the formulas.

Based on the conversion of units for lengths, studied in the chapter, the units of areas can also be converted:

1 cm2 = 100 mm2

1 m2 = 10000 cm2

1 hectare = 10000 m2