Math Puzzle of the Week

January 5, 2009

HAPPY NEW YEAR!
Algebra: The number of days in a non-leap year, 365, is special because it is the sum of 3 squares. What are they?

From the Jordan Middle School Einstein Problem Sets.

Answer available January 12, 2009 next puzzle.

Answer to math puzzle of December 29:

Geometry: A rhombus has sides of length 10 and its diagonals differ by 4. What is its area?

From NCTM

Solution: In a rhombus the diagonals are always at right angles, and they bisect each other. If the shorter of the two diagonals is 2x, and the longer 2x + 4, then the diagonals divide the rhombus into 4 congruent right triangles with sides x and x+2 and each hypotenuse is 10, that is, x² + (x+2)² = 2x² + 4x + 4 = 100 so x = 6, so the area is 2•6•8 = 96

For more math puzzles, check out http://www.mathpuzzle.com/, http://mathschallenge.net/, http://www.princeton.edu/~mathclub/puzzles4.html and http://mathforum.org/k12/k12puzzles/