A box contains 8 white and 4 black balls. The balls are drawn randomly one by one until those of the same colour left
in the box. The probability that they are white, is
A 4-digit number is formed with the digits from 1,2,3,4,5, without repetition. The probability that it is divisible by 3 is
The average marks of boys in a class is 52 and that of girls is 42. The average marks of boys and girls combined is 50.
The percentage of boys in the class is
40%
20%
80%
60%
A bag contains 7 tickets numbered 0,1,2,...6. Four tickets are drawn one by one with replacement. The probability that
the sum of the numbers on them is 8, is
Out of 13 group application for a job, there are 5 women and 8 men. It is desired to select to persons for the job. The
probability that at least one of the selected persons will be a women is
A key bunch contains 10 keys of which only one key can open a door. A man tries to open the door by choosing a
key at random and discarding the wrong key after each trial. The probability that the door is opened in the fifth trial is
A pack of playing cards was found to contain only 51 cards. If the first 13 cards which are examined are all red, Then
the probability that the missing card is black , is
A fair coin is tossed n times. If X is the number of times heads occur and P(X = 4), P(X = 5), P(X = 6) are in AP, then n is equal to
13
7
11
None of these
Twenty five coins are tossed simultaneously. The probability that the fifth coin will fall with head upwards is
One Indian and four American men and their wives are to be seated randomly around a circular table. Then the
conditional probability that the Indian man is seated adjacent to his wife given that each American man is seated
adjacent to his wife, is
