Or search by topic
A pentagon has five diagonals (lines drawn between the corners). You can trace over all of the diagonals without lifting your pencil and without going over any more than once. Try it.
Can the same thing be done with a hexagon (6 sides) or with a heptagon (7 sides)?
(Take care to find ALL the diagonals. Drawing a large shape will help.)
Follow the clues to find the mystery number.
Place the numbers 1, 2, 3,..., 9 one on each square of a 3 by 3 grid so that all the rows and columns add up to a prime number. How many different solutions can you find?
How many different sets of numbers with at least four members can you find in the numbers in this box?