How many different differences can you make?
Can you crack these cryptarithms?
Find the frequency distribution for ordinary English, and use it to help you crack the code.
Think of a two digit number, reverse the digits, and add the numbers together. Something special happens...
A monkey with peaches, keeps a fraction of them each day, gives the rest away, and then eats one. How long can his peaches last?
Can you find a cuboid that has a surface area of exactly 100 square units. Is there more than one? Can you find them all?