Eratosthenes' sieve
JavaScript required *)

Click on any number and all its proper multiples will be removed from the table.

Prime Number Sieve:
Repeat the action:
"Remove all proper multiples of the next remaining number."
Start with the number 2.

When all proper multiples of all numbers in the first row are deleted, the table will contain only primes (except 1).
eratosthenes classroom version  (for MSIE)
classroom gcd-training
  (for MSIE)

multiplication of decimals (interactive)
magic squares (interactive)
Mhb's Math'-pages
zur Seite in deutscher Sprache:
H.B. Meyer, Faust-Gymnasium Staufen)
  *) MSIE recommended