As shown in the figure, the area of the shadow part is 40 square centimeters. How many square centimeters is the area of the big circle larger than that of the small circle?

As shown in the figure, the area of the shadow part is 40 square centimeters. How many square centimeters is the area of the big circle larger than that of the small circle?

Let the radius of the big circle be r, and the radius of the small circle be r. according to the meaning of the question, there are: R2 △ 2-r2 △ 2 = 40 & nbsp; & nbsp; & nbsp; & nbsp; r2-r2 = 80. The area of the big circle is larger than that of the small circle: (r2-r2) × π = 80 × 3.14 = 251.2 (square centimeter) a: the area of the big circle is 251.2 square centimeter larger than that of the small circle

If the area of the shadow is 15 square meters, find the total area of this picture

The area of the great circle is:
15 △ 1 / 8 = 120 (square centimeter)
The area of small circle is:
15 △ 3 / 8 = 40 (cm2)
The total area is:
120 + 40 = 160 (cm2)

As shown in the figure, the radius of the big circle is r, and the area of the small circle is four ninths of the area of the big circle

Where is the picture?
&If I draw a graph like this, I will solve it like this
&Since the radius of the big circle is r, and the area of the small circle is four ninths of that of the big circle, R can be used to represent the radius of the small circle=
πr*2=4/9πR*2   →   r=2/3R    
&So just use the area of the big circle to reduce the area of the shadow and just use the area of the big circle to reduce the surface of the circle;
  
   S-s=πR*2-π（2/3R）*2=5/9πR*2