silly, that's easy! if the last two digits of a number are divisible by four, the whole number is divisible by four; just make sure the third to last digit of said number is even (0 2 4 6 or 8) and then you'll know it's divisible by eight!
yes, i used to be an utter math freak, why do you ask ;) i can tell you verrrrrrry quickly if a number is divisible by 2 (duh), 3 (sum of the digits divisible by 3), 4 (last 2 digits divisible by 4), 5 (0 or 5), 6 (combine the tests for 2 and 3), 8 (see above), and 9 (sum of digits ends up at 9, eventually). there is a special trick for seven but i forget that one :P
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branchandroot
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Date: 2002-07-26 03:54 am (UTC)yes, i used to be an utter math freak, why do you ask ;) i can tell you verrrrrrry quickly if a number is divisible by 2 (duh), 3 (sum of the digits divisible by 3), 4 (last 2 digits divisible by 4), 5 (0 or 5), 6 (combine the tests for 2 and 3), 8 (see above), and 9 (sum of digits ends up at 9, eventually). there is a special trick for seven but i forget that one :P
okay this patterns nerd is going to bed :)