short cut to find the squares

To find the squares of numbers near numbers of which squares are known
For eg you might know squares of 20,30,40,.. Very easily.
So
To find square of 41 which is near to 40, Add 40+41 to 1600 =1681
To find 59²
, which is near to 60, Subtract 60² – (60+59)  =3600-119 = 3481
                                 
Add when the number is more and subtract when the number is less.