EASY
Earn 100

A bag contains 40 tickets numbered from 1 to 40. Two tickets are drawn from the bag without replacement. The probability that the 2nd ticket is a perfect square given that the 1st ticket was a perfect square is

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Important Questions on Probability

EASY
Letters in the word HULULULU are rearranged. The probability of all three L being together is
HARD
A and B are two independent witnesses (i.e., there is no collision between them) in a case. The probability that A will speak the truth is x and the probability that B will speak the truth is y. A and B agree in a certain statement. The probability that the statement is true is
EASY
A die is thrown four times. The probability of getting perfect square in at least one throw is
HARD
An unbiased coin is tossed. If the outcome is a head then a pair of unbiased dice is rolled and the sum of the numbers obtained on them is noted. If the toss of the coin results in tail then a card from a well-shuffled pack of nine cards numbered 1, 2, 3,, 9 is randomly picked and the number on the card is noted. The probability that the noted number is either 7 or 8 is
MEDIUM
A and B are independent events. The probability that both A and B occur is 120 and the probability that neither of them occurs is 35. The probability of occurrence of A is
HARD

A computer producing factory has only two plants T1 and T2. Plant T1 produces 20% and plant T2 produces 80% of the total computers produced. 7% of computers produced in the factory turn out to be defective. The probability that a computer turns out to be defective which is produced in plant T1 is ten times of the computers produced in the plant T2. A computer produced in the factory is randomly selected and it does not turn out to be defective. Then the probability that it is produced in plant T2 is

MEDIUM
A box A contains 2 white, 3 red and 2 black balls. Another box B contains 4 white, 2 red and 3 black balls. If two balls are drawn at random, without replacement from a randomly, selected box and one ball turns out to be white while the other ball turns out to be red, then the probability that both balls are drawn from box B is :
HARD
If the mean and the variance of a binomial variate X  are 2 & 1 respectively, then the probability that X takes a value greater than or equal to one is:
EASY

If A and B are events such that PA=0.42, PB=0.48 and P A and B=0.16. Then,

I. P not A=0.58

II. P not B=0.52

III. P A or B=0.47

MEDIUM
A signal which can be green or red with probability 4 5 and 1 5 respectively, is received by station A and then transmitted to station B . The probability of each station receiving the signal correctly is 3 4 . If the signal received at station B is green, then the probability that the original signal is green, is
HARD
Let X and Y be two events such that PX=13PXY=12 and PY|X=25. Then
HARD
Let n1 & n2 be the number of red and black balls, respectively, in box I. Let n3 & n4 be the number of red and black balls, respectively, in box II. A ball is drawn at random from box I and transferred to box II. If the probability of drawing a red ball from box I, after this transfer, is 13 , then the correct options(s) with the possible values of n1 & n2 is(are)
EASY
An urn contains 5 red and 2 green balls. A ball is drawn at random from the urn. If the drawn ball is green, then a red ball is added to the urn and if the drawn ball is red, then a green ball is added to the urn; the original ball is not returned to the urn. Now, a second ball is drawn at random from it. The probability that the second ball is red, is:
EASY
A coin is tossed three times. If X denotes the absolute difference between the number of heads and the number of tails then PX=1=
HARD

In a random experiment, a fair die is rolled until two fours are obtained in succession. The probability that the experiment will end in the fifth throw of the die is equal to :

EASY
If A and B are events with PAB=34,P A=23 and PAB=14 then PB is
MEDIUM
If a fair coin is tossed 5 times, the probability that heads does not occur two or more times in a row is
EASY
The mean and variance of a random variable X in binomial distribution are 4 and 2 respectively, then PX=1 is
HARD
There are three bags B1,B2 and B3. The bag B1 contains 5 red and 5 green balls, B2 contains 3 red and 5 green balls, and B3 contains 5 red and 3 green balls, Bags B1,B2 and B3 have probabilities 310,310 and 410 respectively of being chosen. A bag is selected at random and a ball is chosen at random from the bag. Then which of the following options is/are correct?
HARD
Let n1 & n2 be the number of red and black balls, respectively, in box I. Let n3 & n4 be the number of red and black balls, respectively, in box II. One of the two boxes, box I and box II, was selected at random and a ball was drawn randomly out of this box. The ball was found to be red. If the probability that this red ball was drawn from box II is 13, then the correct option(s) with the possible values of n1, n2, n3 & n4 is(are)