As we know only square of 4 and 6 having 6 as unit digit. All the other digit doesn't have 6 in unit digit of two digit number.
Square of 4 is = [tex](4)^2 = 16[/tex]
Square of 6 is = [tex](6)^2 = 36[/tex]
So the possible value for tenth digit is 1 and 3.
