PROBLEM:

Find all four-digit numbers which are a complete square and in which the first two digits are equal and the last two digits are also equal.

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- Oct 8th 2007, 07:11 PMedwardteo.368Find 4 digit number
**PROBLEM:**

Find all four-digit numbers which are a complete square and in which the first two digits are equal and the last two digits are also equal. - Oct 8th 2007, 07:26 PMThePerfectHacker
Working mod 100 we have that 44 is the only possibility for x^2 to have two digits. Which means this number AB (where A,B are digits) must end in 44. This means B=2 or B=8. Thus, 12,...,92 and 18,...,98. But since it is 4 digits the only possible choices are 32,...,92 and 38,...,98 and these are easy to check.