If the radius of the circle is increased by 15, its area will be increased by 88 DM2

If the radius of the circle is increased by 15, its area will be increased by 88 DM2

Let the radius of the original circle be x, then π (x + 15) 2 = π x2 + 88, and the solution is x = 200 π. Then π x2 = 200

The area of a circle is 15 square decimeters. If the radius of the circle is increased by 3 times, the area will increase by () square decimeters

If the radius of a circle is three times larger, the area of the circle will be three times the square of 3 (3 * 3 = 9)
Then 15 * 9 - 15 = 120 square decimeters, the area will increase by 120 square decimeters

The diameter of the big circle is 8 cm, and the diameter of the small circle is 2 cm. The area of the big circle is regarded as unit "1". The area of the small circle is smaller than that of the big circle ()

Because s = π R2 is a small circle
So the ratio of the areas is equal to the ratio of the square of the radius
S small: s large = 2 * 2:4 * 4 = 1:4
Because s large = 1, so s small = 1 / 4
So the area of the small circle is 1-1 / 4 smaller than that of the big circle = 3 / 4