Question

Which of the following could be a perfect square?

• A. A number ending in 3 or 7.
• B. A number ending with odd number of zeros.
• C. A number ending with even number of zeros.
• D. A number ending in 2.

Answer 1

The correct option is C A number ending with even number of zeros.

Unit place of any number's square will have 1, 4, 9, 6, 5 or 0. In other words, the unit places of squares will never be 2, 3, 7, 8.

Also, the square of a number having zeros in the end will always have an even number of zeros in it.
For example,
${400}^2=160000$

It should be noted that even number of zeroes could be a perfect square. However, this is not necessary. For example, 2600 is not a perfect square.