A box contains 4 red marbles, 3 green marbles and 2 blue marbles. One marble is removed from the box and then replaced. Another marble is drawn from the box. What is the probability that the first marble is blue and the second marble is green?

Which number produces a rationale number when multiplied by 1/5

If you are dealt 4 cards from a shuffled deck of 52? cards, find the probability that all 4 cards are diamondsdiamonds.

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.