A box contains some black balls and 30 white balls. If the probability of drawing a black ball is two-fifths of a white ball, find the number of black balls in the box.

A bag contains 15 white balls and some black balls. If the probability of drawing a black ball is thrice that of a white ball, find the number of black balls in the bag.

A bag constains white, black and red ball only. A ball is draw at random form the bage. If the probability of getting a white balls is (3)/(10) and that of a black ball is (2)/(5) then find the probability of getting a red ball. If the bag contains 20 black balls, find the total number of balls in the bag.

A bag contains 7 white, 5 black and 4 red balls, find the probability that the balls is white.

A box contains 3 red, 4 black and 5 white balls. Three balls are drawn at random. Then the probability of 2 white balls and 1 red ball is

Ten percent of the black balls were added to twenty percent of the white balls and the balls were 24. Three times the number of black balls exceeds the number of white balls by 20. Find the number of black balls and also, the number of white balls.

A bag contains 6 black and 3 white balls. Another bag contains 5 black and 4 white balls. If one ball is drawn from each bag, find the probability that these tow balls are of the same colour.

From an um containing x white and y-x black balls, n balls have been lost, then probability of drawing a white ball

A bag contains 6 red, 8 black and 4 white balls. A ball is drawn at random. What is the probability that ball drawn is not black?

A bag contains 6 red 8 black and 4 white balls. A ball is drawn at random. What is the probability that ball drawn is not black?

A bag contains 6 red 8 black and 4 white balls. A ball is drawn at random. What is the probability that ball drawn is not black?