As shown in the figure, the area of the circle is 21.98 square centimeters, so how many square centimeters is the area of the square?

As shown in the figure, the area of the circle is 21.98 square centimeters, so how many square centimeters is the area of the square?

Let the radius of the circle be r, then R2 = 21.98 △ 3.14 = 7, the area of the square is 2R × 2R = 4r2 = 4 × 7 = 28 (square centimeter). Answer: the area of the square is 28 square centimeter

The diameter of a circle is 30cm. What is the area of a semicircle?
What about the perimeter?

3.14x(30÷2)²÷2
=3.14x225÷2
=706.5÷2
=353.25cm²
Diameter = 30cm
Circumference of circle = 3.14x30 = 94.2cm
Half of perimeter = 94.2 △ 2 = 47.1cm
Circumference of semicircle = 30 + 47.1 = 77.1cm

Find the area of a circle 1. Known r = 1cm s = 2. Known r = 3cm s = 3. Known d = 8cm s = 4. Known d = 10cm s = 5. Known r = 6cm s=
6. Known C = 12.56cm s=
7. Known C = 31.4cm s=
8. Known C = 18.84cm s=
9. Known C = 6.28 r = s=

.r=1cm S=π=3.14
2. It is known that r = 3cm, s = 3 & # 178; π = 9, π = 28.26
3. Known d = 8cm s = (8 / 2) ^ 2 π = 50.24
It is known that d = 10cm s = (10 / 2) ^ 2 π = 78.5
5. Known r = 6cm, s = 6 ^ 2, π = 113.04
6. Known C = 12.56cm s = (12.56 / π / 2) ^ 2 * π = 4 π = 12.56
7. Known C = 31.4cm s = (31.4 / π / 2) ^ 2 π = 5 ^ 2 * π = 78.5
8. Known C = 18.84cm s = (18.84 / π / 2) ^ 2 π = 28.26
9. Known C = 6.28 r = s=