Page 245 - ICSE Math 7

10. ABCD is a diameter of a circle of radius 6 cm. The lengths AB,
BC and CD are equal. Semicircles are drawn on AB and BD as A B C D
diameters as shown in the given figure. Find the area of the shaded
region. (Take p = 3.14)

11. Two circles are drawn inside a big circle of diameter 24 cm. The
1 2
diameter of the two circles are and of the diameter of the big
3 3
circle as shown in the adjoining figure. Find the ratio of the areas of
the shaded part to the unshaded part of the circle.

12. The adjoining figure represents a rectangular lawn with a
circular flowerbed in the middle. Find:
2 m
(a) the area of the whole land. 5 m
(b) the area of the flowerbed.

(c) the area of the lawn excluding the area of the flowerbed.
(d) the circumference of the flowerbed. 10 m

AT A GLANCE

¾ Perimeter is the length of the boundary of any closed plane figure.
¾ Area is the surface or region enclosed inside a closed boundary.
¾ (a) Perimeter of a rectangle = 2 × (length + breadth)
(b) Perimeter of a square = 4 × side

(c) Area of a rectangle = length × breadth
(d) Area of a square = side × side
1
¾ (a) Area of a triangle = × base × height
2
(b) Area of a parallelogram = base × altitude

¾ (a) Circumference of a circle 2pr = p × d
(b) Area of a circle = pr 2

¾ (a) Area between two rectangles h b
= Area of outer rectangle – area of inner rectangle
= ab – (a – 2h)(b – 2h) a
(b) Area of a circular ring r

= Area of outer circle – area of inner circle O R
2
= pR – pr 2

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