An urn contains 4 balls. Two balls are drawn at random from the urn (without replacement) and are found to be white. What is the probability that all the four balls in the urn are white ?

An urn contains 10 black and 5 white balls. Two balls are drawn from the urn one after the other without replacement. What is the probability that both drawn balls are black?

There are 6 red and 8 green balls in a bag. 5 balls are drawn at random and placed in a red box. The remaining balls are placed in a green box. What is the probability that the number of red balls in the green box plus the number of green balls in the red box is not a prime number?

An urn contains nine balls of which three are ed four are blue two are green . Three balls are drawn at random without replacement from the urn the probability that the three balls have different colours is :

A Bag I contain 3 red and 4 black balls. White bag II contains 5 red 6 black balls. One ball is drawn at random from one of the bags and it is found to be red. Find the probability that it was drawn from bag II.

Two cards drawn at random and without replacement from a pack of 52 playing cards. Find the probability that both the cards are black .

Each of the n urns contains 4 white and 6 black balls. The (n+1) th urn contains 5 white and 5 black balls. One of the n+1 urns is chosen at random and two balls are drawn from it without replacement. Both the balls turn out to be black. If the probability that the (n+1) th urn was chosen to draw the balls is 1/16, then find the value of n .

A bag contains 3 black and 4 white balls. Two balls are drawn one by one at random without replacement. The probability that second drawn ball is white is

A box contains 3 orange balls, 3 green balls and 2 blue balls. Three balls are drawn at random from the box without replacement. The probability of drawing 2 green balls and one blue ball is

A bag A contains 2 white and 3 red balls and a bag B contains 4 white and 5 red balls. One ball is drawn at random from one of the bags and is found to be red. Find the probability that it was drawn from bag B.

A bag containing 5 red and 3 blue balls. If 3 balls are drawn at random without replacement the probability that exactly two of the three balls were red, the first being red is