What the difference between wavelength and frequency

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?

Apack of gum would be considered a(n) necessity luxury item small ticket item unaccountable expense

How can you check that you have correctly converted frequencies to relative frequencies?