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Printjmc
number theory intermediate
Problem
Find all 6-digit multiples of 22 of the form where and are digits. What is the maximum value of ?
Solution
First, since , a number is divisible by if and only if it is divisible by both 2 and 11. is divisible by 2 if and only if is even (=0, 2, 4, 6, or 8). Also, is divisible by 11 if and only if is divisible by 11. Thus, . We are looking to maximize , so we need to minimize . (otherwise , which is not a digit). Thus we take , so the maximum value of is .
Final answer
8