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In the figure (i) given below, ABCD is a square of side 14 cm. A, B, C and D are centres of the equal circles which touch externally in pairs. Find the area of the shaded region.

In the figure, ABCD is a square of side 14 cm. A, B, C and D are centres of the equal circles which touch externally in pairs. Find the area of the shaded region. Mensuration, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Mensuration

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Answer

Let r cm be the radius of each circle.

From figure,

⇒ r + r = AD

⇒ 2r = 14

⇒ r = 7 cm.

Hence, radius of each circle = 7 cm.

Area of each circle = πr2

= 227×(7)2\dfrac{22}{7} \times (7)^2

= 227×7×7\dfrac{22}{7} \times 7 \times 7

= 22 x 7

= 154 cm2.

Area of 4 circles = 4 × 154 = 616 cm2.

From figure,

Radius of each quadrant in square ABCD = 7 cm.

Area of each quadrant = 14πr2\dfrac{1}{4}πr^2

= 14×227×72\dfrac{1}{4} \times \dfrac{22}{7} \times 7^2

= 38.5 cm2.

Area of 4 quadrants = 4 × 38.5 = 154 cm2.

Area of square = (side)2

= (14)2 = 196 cm2.

Area of shaded region = (Area of 4 circles - Area of 4 quadrants) + (Area of square - Area of 4 quadrants)

= (616 - 154) + (196 - 154)

= 462 + 42

= 504 cm2.

Hence, area of shaded region = 504 cm2.

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