Question

method to find the square of a number when unit digits is 9​

Answer 1

Answer:

If a perfect square ends with a 5, then the unit's digit of its square root is definitely 5. If a perfect square ends with a 6, then the unit's digit of its square root has to be either 4 or 6. If a perfect square ends with a 9, then the unit's digit of its square root has to be either 3 or 7.

Answer 2

Answer:

if unit digit is 9

then the square root must be 3 or 7

or

if a number is squared with unit digit 9 then unit digit of square will be 1