Advertisements
Advertisements
Question
A lawn is in the shape of a semi-circle of diameter 42 m. The lawn is surrounded by a flower bed of width 7 m all around. Find the area of the flower bed in m2 .
Solution
Diameter of the inner semi-drde = 42 m
Hence, radius of the inner semi-circle = r = 21 m
Width of the flower bed = 7m
Diameter of the outer semi-circle = ( 42 + 2 x 7) m = 56 m
Hence, radius of the outer semi-circle= R = 28 m
Area of the semicircular flower bed =Area of outer semi-cirde - area of inner semi-drde
`= 1/2 pi "R"^2 - 1/2 pi "r"^2`
`= 1/2 pi ("R"^2 - "r"^2)`
`= 1/2 xx 22/7 xx (28^2 - 21^2)`
`= 1/2 xx 22/7 xx (784 - 441)`
`= 1/2 xx 22/7 xx 343`
= 539 m2
APPEARS IN
RELATED QUESTIONS
In Fig 4, a circle is inscribed in an equilateral triangle ABC of side 12 cm. Find the radius of inscribed circle and the area of the shaded region.[Use π=3.14 and √3=1.73]
The minute hand of clock is10cm long. Find the area of the face of the clock described by the minute hand between 8am and 8:25 am
The wheel of a motor cycle is of radius 35 cm. How many revolutions per minute must the wheel make so as to keep a speed of 66 km/hr ?
Find the length of the arc of a circle of diameter 42 cm which subtends an angle of 60° at the centre.
A wire when bent in the form of an equilateral triangle encloses an area of `121sqrt(3) "cm"^2`. The same wire is bent to form a circle. Find the area enclosed by the circle.
Find the area of a quadrant of a circle whose circumference is 88 cm.
Four equal circles are described about the four corners of a square so that each touches two of the others, as shown in the figure. Find the area of the shaded region, if each side of the square measures 14 cm.
Diameter of the circular garden is 42 m. There is a 3.5 m wide road around the garden. Find the area of the road.
Find the area and perimeter of the following sector :
Radius= 6 cm, angle at the centre is 70°
The shaded portion of the figure, given alongside, shows two concentric circles. If the circumference of the two circles is 396 cm and 374 cm, find the area of the shaded portion.
Draw the circumcircle of Δ PMT in which PM = 5.4, P = 60°, M = 70°.
Construct an angle PQR = 45°. Mark a point S on QR such that QS = 4.5 cm. Construct a circle to touch PQ at Q and also to pass through S.
A wire when bent in the form of a square encloses an area of 484cm2. If the same wire is bent into the form of a circle, find the area of the circle.
A wire bent in the form of an equilateral triangle has an area of `121sqrt(3)"cm"^2`. If the same wire is bent into the form of a circle, find the area enclosed by the wire.
Circumference of a circle is always ______.
The area of a quadrant of a circle whose circumference is 22 cm, is ____________.
A wire is bent to form a square of side 22 cm. If the wire is rebent to form a circle, its radius is ______.
In reference to a circle the value of π is equal to ______.
