A jar contains 54 marbles, each of which some are blue, some are green and some are white. The probability of selecting a blue marble at random is and the probability of selecting a green marble at random is . How many white marble does the jar contain?

Total numbers of elementary events are: 54

Probability of drawing a blue marble = 1/3

Number of blue marbles = 54 x 1/3 = 18

Probability of drawing a green marble = 4/9

Number of green marbles = 54 x 4/9 = 24

Number of white marbles = 54 - (18 + 24) = 54 - 42 = 12.