Question

A bag contains 6 red marbles and 30 white marbles. If a representative sample contains 3 red ​marbles, then how many white marbles would you expect it to​ contain?

Answer 1

there are 36 marbles total.
if the sample contains 3 red marbles, then that is half of the total amount of 6. therefore, half of each color is being taken for the sample. this means that you should expect for there to be 15 while marbles in the sample.