mathematics tricks

squaring a two digit number that begins with a '5'

1-square the first digit
2-add this number to the second number to find the first part of the answer
3-square the second digit: that is the last part of the answer.

Example:what is the square of 58==> 58^2?
5^2=25==>25+8=33 _ _
8^2=64==> 3364Ans.