Is there a rule to test that a number is divisible by 7?? you could maybe call it the magic rule of 7 per say??
2006-10-02 15:06:22 · 3 answers · asked by lint 1 in Education & Reference ➔ Trivia
To find out if a number is divisible by seven, take the last digit, double it, and subtract it from the rest of the number. If you had 203, you would double the last digit to get six, and subtract that from 20 to get 14. If you get an answer divisible by 7 (including zero), then the original number is divisible by seven. If you don't know the new number's divisibility, you can apply the rule again.
2006-10-02 15:14:11 · answer #1 · answered by Ars Magica 5 · 3⤊ 0⤋
Plain ole division? Just divide the number by 7.
2006-10-03 16:19:49 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Don't know a magic rule, but just using 7 times tables would be as quick as your first answer!
2006-10-03 02:36:59 · answer #3 · answered by cloud43 5 · 0⤊ 0⤋