Put a circle into an approximate rectangle, increase the circumference by 4cm, then the circumference of the circle is (), and the area is ()

Put a circle into an approximate rectangle, increase the circumference by 4cm, then the circumference of the circle is (), and the area is ()

When the circumference of a rectangle is increased by 4cm, it means that two radii are increased, 4 △ 2 = 2cm (radius)
3.14 × 2 × 2 = 12.56 cm (perimeter)
3.14 × 2 × 2 = 12.56 square centimeter (area)

Divide a circle into equal parts and form an approximate rectangle. As a result, the circumference of the circle is 1 decimeter less than that of the approximate rectangle. How many square centimeters is the area of the circle

Long π R, wide R
2(πr+r)-2πr=2r=1
r=1/2
S=πr^2=π/4

Cut out the largest circle on a piece of 18 cm long and 112 cm wide rectangular paper. What is the area of this circle in square centimeter? What is the area of the remaining paper in square centimeter?

If the maximum diameter of a circle is 18, then s = π R ^ 2 = 254.47 (approximately equal to)
The remaining s = 18 * 112-254.47 = 1761.53

Cut out the biggest circle from a rectangle of 10 cm long and 4 cm wide. The area of this circle is () square centimeter

The maximum circle diameter is 4cm;
Area = 3.14 × (4 △ 2) &# 178; = 3.14 × 4 = 12.56 square centimeter;
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