Remember this problem? The one where you had to find the area between two circles by only knowing the length of the tangent "chord" (the red line)?

That problem is solved using some (moderately) tricky geometry. But if you know that the problem is solvable, it's actually pretty easy to solve by simply using the formula for the area of the circle and a bit of logic.

Can you do it?

1. Radius of either circle is unknown
2. Area between circles is still solvable

Therefore, the radius of the smaller circle is irrelevent.
Assume smaller's circle radius is zero. Then the tangent becomes the diameter of the larger circle. Now it's just a matter of calculating the area of larger circle with a diameter of 10 inches (length of tangent).

Posted by Happy on 2002-05-10 06:11:59