If the radius of a circle is a centimeter and 2: a = A: 3, the area of the circle is () square centimeter A. 23 π B. 6 π C. 6D

If the radius of a circle is a centimeter and 2: a = A: 3, the area of the circle is () square centimeter A. 23 π B. 6 π C. 6D

2: A = A: 3, a × a = 2 × 3, A2 = 6; therefore, the area of this circle is 6 π

The radius of the circle increased from 4 decimeters to 6 decimeters, and the area of the circle increased______ Square decimeter

3.14 × 62-3.14 × 42 = 3.14 × (36-16) = 3.14 × 20 = 62.8 (bisecting decimeter) a: the area of a circle has increased by 62.8 square decimeters

The circumference of the outer circle of a ring is 25.12 decimeters, the radius of the inner circle is 30 centimeters, and the area of the circle is several square centimeters

Circumference = 25.12 decimeters
Outer circle radius = 25.12 △ 6.28 = 4 decimeters = 40 cm
The area of the ring = 3.14 × (40 × 40-30 × 30) = 2198 square centimeters

The diameter of a circle is 6cm, and the area of the circle is square centimeter. For a ring, the radius of the outer circle is 3DM, the diameter of the inner circle is 4decim, and the area is
To draw a circle with a circumference of 15.7 decimeters, the distance between the two toes of the compass should be decimeters. The circumference of a circle is 9.42 cm. Fold it in half and divide it into two equal parts. The circumference of each part is. Divide a circular piece of paper with a diameter of 8 decimeters into several equal parts to form an approximate rectangle with a radius of width. The circumference of the rectangle is decimeters Determinant determinant determinant determinant

① 3.14 × (6 △ 2) &# 178; = 28.26 square centimeter
② 3.14 × 3 & # 178; - 3.14 × (4 △ 2) &# 178; = 15.7 square decimeters
③ 15.7 ﹣ 3.14 ﹣ 2 = 2.5 decimeters
④ 9.42 △ 2 + 9.42 △ 3.14 = 7.71cm
⑤ 3.14 × (8 ／ 2) &# 178; △ 8 ／ 2) = 12.56 decimeters
12.56 × 2 + (8 △ 2) × 2 = 33.12 decimeters

The radius of a circle is 2 meters. The length of a rectangle is equal to the circumference of the circle, and the width is equal to the diameter of the circle. What is the difference between their areas?

3.14 × 22 = 3.14 × 4 = 12.56 (square meters), (2 × 3.14 × 2) × (2 × 2) = 12.56 × 4 = 50.14 (square meters), 50.24-12.56 = 37.68 (square meters) a: their area difference is 37.68 square meters. So the answer is: 37.68 square meters

If the radius of a circle increases from 2 cm to 6 cm, how many cm does the circumference of the circle increase
It's very urgent

4 times 3.14

The radius of a circle is R. if we increase its radius by 2 cm, how many cm will the circumference of the circle increase?

2π(R+2)-2πR
=2πR+4π-2πR
=4π
The circumference of this circle will increase by 4 π cm

The circumference of a circle is 31.4cm. With one of its diameters as the base, draw the largest triangle in the circle. The area of the triangle is______ Square centimeter (π = 3.14)

The diameter of the circle is: 31.4 △ 3.14 = 10 (CM), the radius of the circle, that is, the height of the triangle is: 10 △ 2 = 5 (CM), and the area of the triangle is: 10 × 5 △ 2 = 25 (square cm); answer: the area of the triangle is 25 square cm. So the answer is: 25

The circumference of a circle is 31.4cm. With one of its diameters as the base, draw the largest triangle in the circle. What is the area of the triangle?

The triangle with the bottom diameter and the high radius has the largest area
Diameter: 31.4 / 3.14 = 10 cm
Radius: 10 / 2 = 5cm
Triangle area: 10 * 5 / 2 = 25 square centimeters

The diameter of the small circle is 6cm, the radius of the big circle is 4cm, the perimeter ratio of the big circle and the small circle is (), and the area ratio is ()

The diameter of the small circle is 6cm, the radius of the big circle is 4cm, the perimeter ratio of the big and small circles is (3:2), and the area ratio is (9:4)