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number theory intermediate
Problem
The base-ten representation for is , where , , and denote digits that are not given. What is ?
(A)
(B)
(C)
(D)
Solution
We can figure out by noticing that will end with zeroes, as there are three factors of in its prime factorization, so there would be 3 powers of 10 meaning it will end in 3 zeros. Next, we use the fact that is a multiple of both and . Their divisibility rules (see Solution 2) tell us that and that . By guess and checking, we see that is a valid solution. Therefore the answer is .
Final answer
C