How about reasoning it out without solving formulas?
If the area of the shaded region is 3 times as much as that of the non-shaded region, then the ratio of the area of the big circle to that of the small circle is 4:1.
Area is based off of the square of the radius... so if the big circle has 4 times the area, it will have root 4 = 2 times the radius.
Since circumference is linear, if the big circle has twice the radius, it will also have twice the circumference.
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
circle
-
Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
-
II
- Master | Next Rank: 500 Posts
- Posts: 400
- Joined: Mon Dec 10, 2007 1:35 pm
- Location: London, UK
- Thanked: 19 times
- GMAT Score:680
A very good point ... and a different way of looking at this !Stuart Kovinsky wrote:How about reasoning it out without solving formulas?
If the area of the shaded region is 3 times as much as that of the non-shaded region, then the ratio of the area of the big circle to that of the small circle is 4:1.
Area is based off of the square of the radius... so if the big circle has 4 times the area, it will have root 4 = 2 times the radius.
Since circumference is linear, if the big circle has twice the radius, it will also have twice the circumference.
