John M. Flanigan <johnf@hawaii.edu> The equation is the final arbiter.
Math Resource Instructor --Werner Heisenberg
Kapi'olani Community College The scoreboard is the final arbiter.
Honolulu, Hawaii --Bill Walton
Rule A number is divisible by:
2 IF the last digit is divisible by 2
3 IF the sum of the digits is divisible by 3
4 IF the last two digits are divisible by 4
5 IF the last digit is divisible by 5 (is 0 or 5)
6 IF the number is divisible by 2 and by 3
7 IF cross out last digit, multiply by 2, subtract from
remaining digits, repeat if possible; the residue is divisible by 7.
8 IF the last three digits are divisible by 8
9 IF the sum of the digits is divisible by 9
10 IF the last digit is divisible by 10 (is 0)
11 IF the alternate sum of the digits is divisible by 11
12 IF the number is divisible by 3 and by 4
13 IF cross out last digit, multiply by 9, subtract from
remaining digits, repeat if possible until the residue is 0 or negative;
the residue is divisible by 13.
14 IF the number is divisible by 2 and by 7
15 IF the number is divisible by 3 and by 5
16 IF the last four digits are divisible by 16
17 IF cross out last digit, multiply by 5, subtract from
remaining digits, repeat if possible until the residue is 0 or negative;
the residue is divisible by 17.
18 IF the number is divisible by 2 and by 9
19 IF cross out last digit, multiply by 17, subtract from
remaining digits, repeat if possible until the residue is 0 or negative;
the residue is divisible by 19.
20 IF the number is divisible by 4 and by 5
21 IF the number is divisible by 3 and by 7
22 IF the number is divisible by 2 and by 11
23 IF cross out last digit, multiply by 16, subtract from
remaining digits, repeat if possible until the residue is 0 or negative;
the residue is divisible by 23.
24 IF the number is divisible by 3 and 8
25 IF the last 2 digits are divisible by 25
26 IF the number is divisible by 3 and 13
27 IF . . . (Does anyone wish to continue the list?)
John M. Flanigan <johnf@hawaii.edu> The equation is the final arbiter.
Math Resource Instructor --Werner Heisenberg
Kapi'olani Community College The scoreboard is the final arbiter.
Honolulu, Hawaii --Bill Walton
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