Squaring 2-digit numbers ending with 5

To square 2-digit numbers ending with 5:    ex.  65×65=4225

-Multiply the tens digit of the number being squared times its next higher digit. This yields the hundreds digit(s) of the answer.    ex.  In (…5,6,7,8…) the next higher digit to 6 is 7, so 6×7=42 for an answer of 42_ _.

-Because 5 is the ones digit being squared, the last two digits of the answer are always 25.    ex.  _ _ 25

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