Help solve this number game of remainders.?

Ask a friend to keep a number less than 1000 in mind.Ask to divide it by 7,11,13.Tell to note down the remainders.You can build the number he had in mind using remainders r1( remainder obtained by dividing by 7), r2 ( remainder obtained by dividing by 11), r3 ( remainder obtained by dividing by 13). Let r1 is multiplied by 715, r2 by 364 and r3 by 924. Add the products and divide the sum by 1001. The remainder you get is the number your friend kept in mind. My question is how were 715, 364 and 924 found? Can sm1 tell me similar number game?