Little rings
Shown in the above figure are three annuli. Each red chord has a length of
. Which has the largest area?
Note:
Each chord is tangent to each inner circle.
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1 solution
Let the radius of large and small circle be r1 and r2
so, r1^2=r2^2+15^2
The area in between two circles
=π(r1^2-r^2)
=π(r2^2+15^2-r2^2)
=225π
therefore the blue, green and yellow portion have same area.