Suppose a jar contains 18 red marbles and 13 blue marbles. If you reach in the jar and pull out 2 marbles at random at the same time, find the probability that both are red.

In a box there are 3 red, 4 blue, and 5 white marbles.  If 3 marbles are selected at random and the colors are noted, find the probability that all are white given that all are the same color.

The mean weight of a Great Dane is 63.0 kg with a standard deviation of 2.3 kg.  Suppose a researcher randomly samples 61 Great Danes and records the weights of the sampled dogs.  Calculate the standard deviation of the mean, rounded to 2 decimal places

A jar contains 2 red marbles, 8 green marbles, and 5 blue marbles. What is the probability that you draw 3 green marbles in a row if you do replace the marbles after each draw? =  What is the probability that you draw 6 blue marbles in a row if you don't replace the marbles after each draw?

Suppose a jar contains 9 red marbles and 37 blue marbles. If you reach in the jar and pull out 2 marbles at random at the same time, find the probability that both are red.