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jmc

number theory senior

Problem

Consider the following two strings of digits: and . First consider them to be in base and sum them to get . Then consider them to be in binary, sum them, write the answer in binary, then interpret the digits of the sum as if they were in base to get . What is ?
Solution
If you notice carefully, the two sequences of digits never both have a in the same place. Thus, whether you add them in base or binary, the resulting sequence of digits is the same. Thus whether we add them in base or add them in binary and interpret the digits in base , we get the same result, so the difference is .
Final answer
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