2023 AMC 8 Problems/Problem 12
Contents
Problem
The figure below shows a large white circle with a number of smaller white and shaded circles in its interior. What fraction of the interior of the large white circle is shaded?
Solution 1
First, the total area of the radius circle is simply just
when using our area of a circle formula.
Now from here, we have to find our shaded area. This can be done by adding the areas of the
-radius circles and add; then, take the area of the
radius circle and subtract that from the area of the
radius 1 circles to get our resulting complex area shape. Adding these up, we will get
.
So, our answer is .
~apex304
Solution 2
Pretend each circle is a square. The second largest circle is a square with area and there are two squares in that square that each has areas of
which add up to
. Subtracting the medium-sized squares' areas from the second-largest square's area, we have
. The largest circle becomes a square that has area
, and the three smallest circles become three squares with area
and add up to
. Adding the areas of the shaded regions, we get
, so our answer is
.
-claregu LaTeX (edits -apex304)
Video Solution (Animated)
~Star League (https://starleague.us)
Video Solution by Magic Square
https://youtu.be/-N46BeEKaCQ?t=4590
Video Solution by SpreadTheMathLove
https://www.youtube.com/watch?v=UWoUhV5T92Y
Video Solution by Interstigation
https://youtu.be/1bA7fD7Lg54?t=854
See Also
2023 AMC 8 (Problems • Answer Key • Resources) | ||
Preceded by Problem 11 |
Followed by Problem 13 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AJHSME/AMC 8 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.