324
(i) Unit place of 324 is 4. So it is a perfect square number.
(ii) Sum of digits = 3 + 2 + 4 = 9 which is perfect square.
(iii) This number will have two digits in square root.
(iv) Making pair of 2-2 in 324 from right to left, second pair has only one digit 3.
∴ Tens place in square root of 324 will be 1.
(v) ∵ Extreme digit of number 324 is 3.
∴ Extreme digit of square root will be either 1 or 8.
Hence, the square root of 324 is 18.