Math is full of symbols: lines, dots, arrows, English letters, Greek letters, superscripts, subscripts ... it can look like an illegible jumble. Where did all of these symbols come from? | TED-Ed

This has been called one of the hardest logic puzzles in the world. Can you solve it? Find out the answer here: http://ow.ly/Ooxta | TED-Ed

Celebrate Leap Day with this challenging frog riddle! Find out the answer here: http://t.ted.com/zcOqMwh | TED-Ed