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jmc

prealgebra senior

Problem

Let be a positive number such that when is divided by , the remainder is Compute the sum of all possible two-digit values of .
Solution
If 4 is subtracted from 109, the result is 105. Then each of the two-digit numbers that will divide 109 with a remainder of 4 will divide 105 exactly. Thus, the problem is equivalent to finding all two-digit divisors of 105. Since the prime factors of 105 are 3, 5, and 7, the divisors are , , and , or with a sum of .
Final answer
71