Emerging Trends E-Newsletter
Fire Protection Engineering - The Official Magazine of the Society of Fire Protection Engineers
 
:: BRAINTEASER ::      

If a cube has sides with a length of "X", what is the length of the interior diagonal of the cube?


A square is circumscribed within a circle, which is in turn circumscribed within another square as shown below.

Which area is larger - area "A" or area "B"?

If a side of the largest square has length "S," then the largest square has an area of S2. Also, the circle has an area of Π/4S2.

The radius of the circle is 1/2 S. The length of a side of the smaller square is 2a. The length of a can be found using the Pythagorean theorem:

a2 + a2= (1/2 S)2.

Solving for a yields a = S 1/8. Therefore, the area of the small square is (2a)2= (2S 1/8)2= 1/2 S2.

The area "A" is equal to 1/4 (S2 - Π/4S2) = 1/4S2 (1- Π/4), and the area "B" is equal to 1/4(Π/4S2 - 1/2 S2) = 1/4 S2 (Π/4 -1/2). Therefore, the area "B" is larger than the area "A".

About | Site Map | Privacy Statement | Terms of Use
Copyright © 2010 Penton Media, Inc.