Who's up for two difficult math questions??

WedgeDawg
Tue, 23 Nov 2010 14:56:18 +0000

For number 20:
Radius of large circle x4 = side of square

Side of square = 4

Now find the diagonal of the square via Pythagorean theorem:

sqrt(4^2 + 4^2) = sqrt(32) = 4sqrt(2)

Half the diagonal is 2sqrt(2).

2sqrt(2) - diameter of big circle = diameter of small circle

2sqrt(2) - 2 = diameter of small circle

we need radius of small circle so divide that by two

Answer is sqrt(2) - 1 or D

For the second one, xiggi’s method is the most reliable. Princeton R and Kaplan have other ways of tackling it, but they are longer and it boils down to the same thing.