Mathematics
Find the perimeter and area of the shaded region shown in the figure. The four corners are circle quadrants and at the centre, there is a circle.

Mensuration
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Answer
4 quadrants = 1 full circle
Circumference of circle = 2πr
= 2 × 3.14 × 1
= 6.28 cm.
Length of each shaded straight sides = 4 - 1 - 1 = 2 cm.
Total length = 4 × 2 = 8 cm.
Central circle boundary :
radius = = 1 cm.
Circumference of circle = 2πr
= 2 × 3.14 × 1
= 6.28 cm.
Total perimeter = 6.28 + 8 + 6.28 = 20.56 cm.
Area of shaded region = Area of the square - (Area removed at the corners - Area of central circle)
Area of square = (side)2 = 42 = 16 cm2.
Area removed at the corners :
Area of 1 quadrant = πr2
= × 3.14 × 12 = 0.785
∴ For 4 quadrants = 4 × 0.785 = 3.14 cm2.
Area of central circle = πr2
= 3.14 × 12 = 3.14 cm2.
Area of shaded region = Area of square - Area of central circle - Area of 4 quadrants
= 4 × 4 - (3.14 + 3.14)
= 16 - 6.28 = 9.72 cm2.
Hence, perimeter = 20.56 cm and area of shaded region = 9.72 cm2.
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