National Council of Teachers of Mathematics
Nctm: Figure This: Upside Down (Pdf)
What lowercase letters read the same both upside down and right side up? If you have the answer, then you can handle this geometric symmetry math challenge. A one-page activity from the NTCM Math Challenge for Families collection....
Khan Academy
Khan Academy: Hands on Activity
This is a hands on activity asks students to design and build a certain number dinosaur parts in order to create a crowd of a given size. Apply combinatorics to design your own crowd of dinosaurs. Click on First Lesson before you begin...
Harvey Mudd College
Mudd Math Fun Facts: Magic Squares, Indeed!
This tutorial provides a definition and examples of a "magic square" and then shows a proof and generalizations.
Harvey Mudd College
Mudd Math Fun Facts: Squares Ending in 5
This math tutorial features an exercise in which you are given any two-digit number that ends in 5 and then square it in your head.
ACT360 Media
Act Den: Math Den
[Free Registration/Login Required] This website is geared mainly towards students age 12-18, but the Math Challenge problems are great for some elementary students also.