Discussion
In the figure shown, the radius of the larger circle is twice that of the smaller circle. If the circles are concentric, what is the ratio of the shaded region’s area to the area of the smaller circle? 
*This question is included in Nova Press: Set F - Geometry, question #16
| (A) | 10:1 |
| (B) | ... |
| (C) | ... |
| (D) | ... |
| (E) | ... |
| (F) | ... |
The solution is
Posted: 12/20/2012 10:03
What if you substituted for radius 4 for the larger circle and radius 2 for the smaller ? You get 8:1 ?!?
Posted: 12/21/2012 16:32
Abdulla, the shaded area = (Area of the Large circle - Area of the Smaller circle). Using your numbers, it will be = π16 - π4 = 12π. The inner circle's area = 4π. The ratio between the two = 12 : 4 or 3:1.