A fruit seller on purchased 300 oranges at 6 for a dollar. He sold them at 5 for a dollar. what is his percentage gain?

If you roll two fair dice (one black die and one white die), in how many ways can you obtain a 4 on at least one die?

Is the square root of 4 plus the square root of 16 rational?

There are three bags: a (contains 2 white and 4 red balls), b (8 white, 4 red) and c (1 white 3 red). you select one ball at random from each bag, observe that exactly two are white, but forget which ball came from which bag. what is the probability that you selected a white ball from bag a?