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Question -

The area of anequilateral triangle ABC is 17320.5 cm2. With each vertex of thetriangle as centre, a circle is drawn with radius equal to half the length ofthe side of the triangle (see Fig. 12.28). 



Answer -

Find the area of the shaded region. (Use π = 3.14 and √3 = 1.73205)

Solution:

ABC is an equilateral triangle.

A = B = C = 60°

There are three sectors each making 60°.

Area of ΔABC = 17320.5 cm2

√3/4 ×(side)2 = 17320.5

(side)2 =17320.5×4/1.73205

(side)2 = 4×104

side = 200 cm

Radius of the circles = 200/2 cm = 100 cm

Area of the sector = (60°/360°)×π rcm2

= 1/6×3.14×(100)cm2

= 15700/3cm2

Area of 3 sectors = 3×15700/3 = 15700 cm2

Thus, area of the shaded region = Area ofequilateral triangle ABC – Area of 3 sectors

= 17320.5-15700 cm= 1620.5cm2


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