35 cm

40 cm

Area of rectangle = length × breadth

Area of cardboard = 40 cm × 35 cm = 1400 cm²

Area of picture = 30 cm × 25 cm= 750 cm²

Area of cardboard not covered by the picture = 1400 cm² - 750 cm²

= 650 cm²

25 cm

30 cm

1. A picture 30 cm by 25 cm is mounted on a cardboard 40 cm by 35 cm. Find the area of the cardboard not covered by the picture.

6 cm

4 cmCM

A

2 cm

8 cm CB

A

2. Find the area of the shaded part of the isosceles triangle ABC of height 6 cm and base 8 cm. The length of each side of the square is 2 cm.

Area of triangle = ½ × base × height

Area of triangle AMC = ½ × 4 cm × 6 cm= 12 cm²

Area of triangle ABC = 2 × 12 (isosceles triangle)= 24 cm²

Area of square = length × length = 2 cm × 2 cm= 4 cm²

Area of shaded part of the isosceles triangle = area of triangle ABC – area of square= 24 cm² - 4 cm² = 20 cm²

6 cm

3. Find the area of the shaded portion.

(π = 22/7 )Area of square = length × length

= 14 cm × 14 cm= 196 cm²

radius of circle = 14/2

= 7 cm

Area of ½ a circle = ½πr²= ½ × 22/7 × 7 cm × 7 cm= 77 cm²

Area of the shaded portion = area of square – area of ½ a circle

= 196 cm² - 77 cm²= 119 cm²

14 cm

14 cm