On a square board, it is the largest circle next to it. The perimeter of the board is known to be 120 decimeters. How many square decimeters is the area of this circle?

On a square board, it is the largest circle next to it. The perimeter of the board is known to be 120 decimeters. How many square decimeters is the area of this circle?

The perimeter of the board is 120 decimeters, so the side length is 120 △ 4 = 30 (decimeters)
Taking 30 decimeters as diameter and radius as 15, the area of circle is 15 × 15 × π ≈ 15 × 15 × 3.14 = 706.5 (square decimeters)

The area of a rectangle and a square is 1225 square centimeters, and that of a circle is 1256 square centimeters?

Circumference = 2 π r = 2x3.14x20 = 125.6cm
Square perimeter = 4 times the root 1225 = 140 cm
Rectangle circumference = 2 (x + y)
xy=1225
When the circumference of a rectangle - the circumference of a square
The solution is y ^ 2-70y + 1225
（y-35）^2≥0
So the circumference of a rectangle is greater than that of a square and greater than that of a circle

The area of a rectangle and a square is 1225cm2, and that of a circle is 1256cm2? Which is the smallest? If the areas of these three figures are equal, can you find the size relationship between their girths?

The area of a rectangle and a square is 1225cm2, and that of a circle is 1256cm2. The maximum perimeter of the three figures is rectangle, and the minimum is circle. When the area of the three figures is equal, the relationship of their perimeter is reversed, that is, rectangle > square > circle

There are big and small circles. The circumference of the big circle is 18.84 meters. The diameter of the big circle is twice that of the small circle. What is the area of the small circle?

The circumference of the great circle is 18.84 meters, and the diameter of the great circle is 18.84 △ 3.14 = 6 meters,
Small circle diameter: 3M, radius: 1.5m, area: 3.14 × 1.5 # 178; = 3.14 × 2.25 = 7.065m # 178;

The diameter of the small circle is equal to the radius of the big circle. The sum of the circumference of the two circles is 18.84 cm. What is the area of the big circle?

Let R be the radius of the big circle and R / 2 be the radius of the small circle
According to the circumference of two circles and L = π (R + R / 2) = 3 π R / 2 = 18.84, r = 2L / (3 π) = 2 × 18.84 / (3 × 3.14) = 4cm,
So the area of great circle s = π R ^ 2 = 3.14 × 4 ^ 2 = 50.24cm2

It is known that the radius ratio of the small circle to the large circle is 3:4, the perimeter of the small circle is 18.84 cm, and the area of the large circle is () cm

The circumference of the small circle is 18.84 cm, and the radius r = 3, that is, the radius of the big circle is 4, and the area s = π R & # 178; = 16 π = 50.24 CM & # 178;

When the area of a square is the same as that of a circle, which figure has a longer perimeter?

If a, the radius of the circle is r
Then a ^ 2 = π R ^ 2
∴a=√π r ＞r
Square circumference

Use a 25.12 decimeter wire to form a circle. The area of the circle is______ ．

(1) The radius of the circle is: 25.12 △ 3.14 △ 2 = 4 (decimeter) the area of the circle is: 3.14 × 42 = 50.24 (square decimeter) answer: the area of the circle is 50.24 square decimeter. So the answer is: 50.24 square decimeter

Take a 12.56 decimeter long wire, first encircle the city into a circle, and then encircle it into a square. Who has the largest area and how much?

Side length of square: 12.56 △ 4 = 3.14
Square area: 3.14x3.14 = 9.8596 (square decimeter)
Diameter: 12.56 △ 3.14 = 4 (decimeter)
Radius: 4 △ 2 = 2 (decimeter)
Area of circle: 3.14x2 & # 178; = 12.56 (square decimeter)
The area of circle is large, large: 12.56-9.8596 = 2.7004 (square decimeter))

A wire can be used to form a square with a side length of 12.56 meters. If this wire is used to form a circle, what is the area of the circle?

Circumference of circle = circumference of square = 12.56 * 4 = 50.24m
Circumference of circle = 2 * 3.14 * r = 50.24
Radius of circle = 50.24 / (2 * 3.14) = 8M
Area of circle = 3.14 * r * r = 3.14 * 64 = 200.96 square meters