Is there a rule to test that a number is divisible by 78?? The magic rule for 7??
2006-10-02 15:01:45 · 4 answers · asked by lint 1 in Education & Reference ➔ Trivia
Sorry not 78 but 7!!
2006-10-02 15:02:21 · update #1
I dont think there is one.
2006-10-02 15:03:00 · answer #1 · answered by Anonymous · 0⤊ 0⤋
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 22:05:38 · answer #2 · answered by Ars Magica 5 · 2⤊ 0⤋
I'll have to remember that one. Good 1 Ars Magica
I knew about 2,3,4,5,6,8,9,10,11,12 ... but not 7
2006-10-02 22:13:47 · answer #3 · answered by upf_geelong 3 · 0⤊ 0⤋
no, it's a prime number
2006-10-02 22:09:21 · answer #4 · answered by james w 3 · 0⤊ 0⤋