In a college, the ratio of boys to girls is 29 : 33 respectively. When 142 more boys join the college, this ratio becomes 21 :19. How many more girls should join the college to make the number of boys and girls equal?
Study the information carefully to answer the following questions: An urn contains 5 red, 3 green, 2 blue and 4 yellow marbles. If three marbles are picked at random, what is the probability that one is green and two are yellow?