#### Answer

A perfect square is a number whose square root is a whole number (is a square of a whole number). 25 is a perfect square because its square root is 5, whereas 50 does not have a whole number as a square root.

#### Work Step by Step

The square root of 25 is 5, a whole number, because 5^2 = 5 x 5 = 25. The square root of 50 is 7.07, which is not a whole number. According to the definition of perfect squares, 25 is a perfect square but 50 is not a perfect square.