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In the figure (i) given below, ABCD is a square of side 14 cm and APD and BPC are semicircles. Find the area and the perimeter of the shaded region.

In the figure, ABCD is a square of side 14 cm and APD and BPC are semicircles. Find the area and the perimeter of the shaded region. Mensuration, ML Aggarwal Understanding Mathematics Solutions ICSE Class 9.

Mensuration

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Answer

Area of square = (side)2 = 142 = 196 cm2.

From figure,

Diameter of both semicircle = side of square = 14 cm.

∴ Radius (r) = 142\dfrac{14}{2} = 7 cm.

Area of both the semi-circles = 2×πr222 \times \dfrac{πr^2}{2}

=2×227×722=2×22×497×2=22×7=154 cm2.= 2 \times \dfrac{\dfrac{22}{7} \times 7^2}{2} \\[1em] = 2 \times \dfrac{22 \times 49}{7 \times 2} \\[1em] = 22 \times 7 \\[1em] = 154 \text{ cm}^2.

Area of shaded region = Area of square - Area of semi-circles

= 196 - 154 = 42 cm2.

From figure,

Perimeter = arc DPA + DC + arc CPB + AB

= πr + 14 + πr + 14

= 2πr + 28

= 2×227×72 \times \dfrac{22}{7} \times 7 + 28

= 44 + 28 = 72 cm.

Hence, area of shaded region = 42 cm2 and perimeter = 72 cm.

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