That&#x27;s why it&#x27;s an abuse of the &quot;number close to 50&quot; trick. It really is meant for single digit differences from 50. The only reason it works for 75 is because hopefully 25^2 comes up often enough that people have it memorized. I know I memorized it long ago after seeing it a number of times: &quot;twenty-five times twenty-five? six twenty-five&quot; is easy for me to remember. If people don&#x27;t have 25^2 memorized, the trick kind of falls down.<p>Otherwise, you&#x27;re right. You can break down the square of <i>any</i> number into (x+y)(x+y) = x^2 + 2xy + y^2. For 50, the &quot;2x&quot; term equals 100, and multiplying by 100 and adding to 2500 is dirt simple for anybody to do.