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A three digit number can be divided by nine. After removing its last digit, the resulting two digit number is a multiple of 17? ... I just need the formula. I know it's 855!
eight hundred and fifty-five
Consider this: the maximum number of 2 digits divisible by 17 is 85
Whether a number can be divided by 9 depends on whether the sum of the numbers of each digit is 9 (if you add it to two, you can add ten digits). If it is 9, you can divide it
8 + 5 = 13, 1 + 3 = 4, the number whose tens are 8 and 5 must be 5 to be divisible by 9 (4 + 5 = 9)
So the answer is 855
Try to prove: any four digit positive integer, if the sum of four digits is a multiple of 9, then the four digit must be divisible by 9, and extend it to n-digit positive integer
If a + B + C + D can be divided by 9 and a + B + C + D = 9m (M is a non negative integer), then the four digit value is 1000A + 100b + 10C + D = 999a + 99b + 9C + (a + B + C + D) = 9 (111a + 11b + C) + 9m
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