*Note: Pretty much any time you have a shaded region problem, you should be thinking about it in 3 parts, arranged into this equation:*

In this particular question, we're going to need to do a little work before we can use that, and then a teensie bit more once we have. We already know the shaded region's area is 64π. We know the smaller circle has a radius of 6, so we can use

*A*= π

*r*

^{2}to find the area of that inner circle (the UNSHADED part) to be 36π.

Put those into the equation above and you get:

**64π + 36π = 100π**

So the area of the WHOLE THING is 100π. Use

*A*= π

*r*

^{2}one more time now to find the radius of the large circle:

100π = π

*r*^{2}100 =

*r*^{2}**10 =**

**r**
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