RWM Geometry 9.10 area of shaded region #14



How is #14 on section 9.10 figured out? Thanks.


I don’t get the given answer, either. Because the diagram is a little ambiguous (which length is “3”?), I tried 3, 6, and 12 for the radius of the larger circle – no luck with any of those, but I’m working with a phone calculator, no paper, and might have made some mistakes.

For the sake of clarity, the process I’m using to get my answers is:
[area of larger circle] - [area of smaller circle] * [0.75]

So, if you’re using the same radii as I am and following the same process and not getting the given answer, the key might just be wrong.

For others who want to take a look, see question 14 in Review:

And here’s the given answer:

Click to show