Hi Sherrie.
When you multiply 7 x 11 x 13, you get 1 001. That's 1000 + 1. So when you multiply a three digit number (let's write it as "abc") by this, then abc (1000 + 1) = abc x 1000 + abc x 1 = abc 000 + abc = abcabc.
You can do something similar. Take a three digit number, multiply by 333 667, then multiply by 3.
Stephen La Rocque.>
