Which is NOT a perfect square

The number if marbles of different colors stored in a hat is listed below: 4 red marbles 10 green marbles 7 blue marbles. without looking in the hat, dan takes out a marble at random. he replaces the marble and then takes out another marble from the hat. what is the probability that dan takes out a blue marble in both draws?

The square pyramid has a volume of 441 cubic inches. what is the value of x? 1/7x is the height x is the base

The standard deviation for a set of data is 5.5. the mean is 265. what is the margin of error?