There are two circles, big and small. The area difference between them is 62.8 square decimeters, and the radius of the big circle is 1.5 times that of the small circle? There are two circles, big and small. The difference of their area is 62.8 square decimeters, and the radius of big circle is 1.5 times that of small circle

There are two circles, big and small. The area difference between them is 62.8 square decimeters, and the radius of the big circle is 1.5 times that of the small circle? There are two circles, big and small. The difference of their area is 62.8 square decimeters, and the radius of big circle is 1.5 times that of small circle

Suppose that the radius of the big circle is r, and the radius of the small circle is R. from the title: π R2 - π R2 = 62.8, r2-r2 = 20, and R = 1.5R, then: (1.5R) 2-r2 = 20, the solution is r = 4, r = 6. Therefore, the area of the big circle is 3.14x36 = 113.04 square decimeters, and the area of the small circle is 3.14x16 = 50.24 square decimeters

Known shadow area is 20 square decimeters, ring area

Let R be the radius of the big circle and R be the radius of the small circle. According to the meaning of the question, r2-r2 = 20 (square decimeter), so the area of the ring is 3.14 × 20 = 62.8 (square decimeter). A: the area of the ring is 62.8 square decimeter

The area of the shadow is 40 square decimeters. Find the area of the ring

Let the radius of the outer circle be r, and the radius of the inner circle be r. from the figure, we can see that the side length of the large square is equal to R, and the side length of the small square is equal to R. the area of the shadow part is 40 square decimeters, that is, r2-r2 = 40. So the area of the ring is: 3.14 × 40 = 125.6 (square centimeter). A: the area of the ring is 125.6 square centimeter