A fair coin is tossed n times. If the probability that head occurs 6 times is equal to the probability that occurs 8 times, then value of n is


Correct option is


Let X be the number of times head occurs. Then X follows a binomial distribution with parameter n and p = 1/2. We are given that 

P(X = 6) =P(X = 8).



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


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


There are two balls in an urn whose colours are not known (each ball can be either white or black). A white ball is put into the urn. A ball is drawn from the urn. The probability that it is white is


A natural number x is chosen at random from the first one hundred natural numbers. The probability that   is


An experiment has 10 equally likely outcomes. Let A and B two non – empty events of the experiment. If a consists of 4 outcomes, the number of outcomes that B must have so that A and B are independent, is


If AB and C are the events such that P(B) = 3/4, P(A ∩ B ∩ C’) = 1/3P(A’ ∩ B ∩ C’) = 1/3, then P (B ∩ C) is equal to


A person writes 4 letters and addresses on 4 envelopes. If the letters are placed in the envelopes at random, the probability that not all letters are placed in correct envelopes is