A bag contains `W` white and 3 black balls. Balls are drawn one by one without replacement till all the black balls are drawn. Then find the probability that this procedure for drawing the balls will come to an end at the rth draw.

A bag contains 10 white and 3 black balls. Balls are drawn one-by-one without replacement till all the black balls are drawn. The probability that the procedure of drawing balls will come to an end at the seventh draw, is

A bag contains 5 white,7 red and 3 black balls.If three balls are drawn one by one without replacement,find the probability that none is red.

A bag contains 5 white; 7red and 4 black balls. If four balls are drawn one by one with replacement; what is the probability that none is white?

A bag contains 5 white,7 red and 8 black balls.Four balls are drawn one by one with replacement,what is the probability that at least one is white?

A bag contains 5 white,7 red and 4 black balls.If four balls are drawn one by one with replacement,what is the probability that none is white?

Consider a bag containing 10 balls of which a few are black balls. Probability that bag contains exactly 3 black balls is 0.6 and probability of bag containing exactly 1 black ball is 0.4. Now, balls are drawn from the bag, one at a time, with out replacement, till all black balls have been drawn.Find the probability that this procedure would end at the 6^(th) draw.

A bag contains 5 white; 7 red and 8 black balls.If four balls are drawn one by one without replacement; find the probability of getting all white balls.

A bag contains 4 green and 6 white balls. Two balls are drawn one by one without replacement. If the second ball drawn is white, what is the probability that the first ball drawn is also white ?

A bag contains 5 white,7 red and 8 black balls.If four balls are drawn one by one without replacement,find the probability of getting all white balls.

A bag contains 5 white, 4 black and 2 red balls. Balls are drawn one by one without replacement. The probability that the 5^("th") ball is a red ball, is