the area of a semi- circle is 27.72 cm². Find its perimeter.
21.6 cm
27.6 cm
25.4cm
Answers
Answer:
21.6
Step by step :
Here Area of Semi-Circle given = 27.72 cm²
But we know that Area of Circle = π(radius)²
∴ Area of Semi-circle = π (radius)² /2
∴ π (radius)²/2 = 27.72
[Putting value of π =22/7 and transposing values to other side]
radius² = (27.72 × 2 × 7)/22
radius² = 17.64
Radius² = (4.2)²
radius = 4.2 cm -------- ( i )
Now
We know that circumference of the circle = 2π×radius
∴ circumference of semi circle = π × radius
Observe the attached figure. You can see that
Perimeter of Semi Circle = Half Circumference of Circle + Diameter
∴ Perimeter of Semi Circle = π × radius + 2 × radius [∵diameter = 2 × radius]
Putting values of π and radius
= (22 × 4.2)/7 + 2 × 4.2
= 22 × 0.6 + 8.4
= 13.2 + 8.4
= 21.6 cm
∴ Perimeter of Semi Circle = 21.6 cm
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