Question

Without doing any calculation, find the number which are surely not perfect squares.

1. 153
2. 257
3. 408
4. 441

Answer 1

The perfect squares of a number can end with any of the digits 0, 1, 4, 5, 6, or 9 at the unit's place. Also, a perfect square will end with an even number of zeroes, if any.

1. Since the number 153 has its unit’s place digit as 3, it is not a perfect square.
2. Since the number 257 has its unit’s place digit as 7, it is not a perfect square.
3. Since the number 408 has its unit’s place digit as 8, it is not a perfect square.
4. Since the number 441 has its unit’s place digit as 1, it is a perfect square.