The probability that a student is not a swimmer is 1/5. The probability that out of 5 students exactly 4 is swimmer is


Correct option is

Let p = probability that a student selected at random is a swimmer = 1 – 1/5 = 4/5.

             n = number of students selected = 5

and       X = number of swimmers

Then X – B (np) when n = 5 and p = 4/5 probability that exactly 4 students are swimmer is




If two events A and B such that P(A’) = 0.3, P(B) = 0.5 and P(A  B) = 0.3, then  is


Seven white bails and three black balls are randomly placed in a row. The probability that no two black balls are placed adjacently equals


If from each of the three boxes containing 3 white and 1 black, 2 white and 2 black, 1 white and 3 black balls, one ball is drawn at random, then the probability that two white and one black ball will be drawn is


There are four machines and it is known that exactly two of them are faulty. They are tested, one by one, in a random order till both the faulty machines are identified. Then the probability that only two tests are needed is


A group of 2n boys and 2n girls is randomly divided into two equal groups. The probability that each group contains the same number of boys and girls is


Let A and B be two events such that P(A) = 0.3 and P(A  B) = 0.8. If Aand B are independent events, then P(B) is


An unbiased dia with faces marked 1, 2, 3, 4, 5 and 6 is rolled four times out of the four faces obtained, the probability that the minimum value is exactly than 2 and the maximum value is exactly 5 is


A pair of unbiased dice is rolled together till a sum of either 5 or 7 is obtained. The probability that 5 comes before 7 is


Each of two persons A and B toss three fair coins. The probability that both get the same number of heads is


Six distinct numbers are selected from first 150 natural numbers. The probability all the six numbers are divisible both by 3 and 5 is