Which is a perfect square? 20 21 24 25

You can find a perfect square when that number can be square rooted and the result is a whole number.  So, the square root of 20 is approximately 4.47; the square root of 21 is approximately 4.58; the square root of 24 is approximately 4.90. The square root of 25 is 5 - a whole number.

25 is a perfect square

5 x 5 = 25

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