Circular metal grills

[maihuna]

HiI saw this question in gmatprep and did wrong : I dont have all the option but was puzzled not seeing the mine calculation:

A circular garment of radius r is surrounded by some metallic construction of width. Find the area of the metallic stuff...

[BuckeyeT]

Sounds like a typical problem from GMAT prep materials of a circle within a circle.

There's a recent explanation in the problem solving section:
https://www.beatthegmat.com/geometry-con ... 29684.html

If that's not what you need, please add a more specific question.