Today I gave my kids the "four fours" challenge. Here it is:
Find a mathematical expression for all the numbers from zero to twenty using common symbols (+, -, x, ÷, √, and !), parentheses, and exactly four 4s. The simpler the expression, the better.
To get you started:
I had to teach my daughter what √4 and 4! mean. She was very motivated to learn them because they were a great tool to solve the challenge.
It turns out that "four fours" is a common challenge, but I found it in Jo Boaler's excellent What's Math Got to Do with It?: How Parents and Teachers Can Help Children Learn to Love Their Least Favorite Subject (amazon affiliate link). The book is full of research-backed suggestions for parents and teachers to help their kids thrive in math. Dr. Boaler will be teaching a course called "How to Learn Math" on Stanford University's free online platform. It's from July 15 to September 27, 2013. You can find out more about it here. I'll be taking the course. Please let me know if you will be.