CBSE Guess > Papers > Important Questions > Class XII > 2011 > Maths > Maths By Mrs. E.Praveen
CBSE CLASS XII
  
Probability
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Bt - BayesTheorem;
Pdt -Probability Distribution
Bd - Binomial Distribution
- An unbiased dice is thrown three times. Getting 3 or 5 is considered as success. Find the probability of at least two successes. BD
- An urn contains seven white, 5 black and 3 red balls. Two balls are drawn at random.
Find the probability that :
i. Both the balls are red.
ii. One ball is red and other is black.
iii. One ball is white.
- 3 cards are drawn at random from a pack of well shuffled 52 cards. Find the probability that :
i. All the three cards are of same suit.
ii. One is a king; the other is a queen and third is a jack.
- There are two bags I and II. Bag I contains 3 white and 2 red balls, bag II contains2 white and 4 red balls. A ball is transferred from bag I to bag II (without seeing its colour) and then ball is drawn from bag II. Find the probability of getting a red ball.
- Bag I contains 3 red and 4 black balls and bag II contains 4 red and 5 black balls. One ball is transferred from bag I to bag II and then a ball is drawn from bag II. The ball so drawn is found to be red in colour. Find the probability that the transferred ball is black. BT
- A problem in mathematics is given to three students whose chances of solving it are 1/2, 1/3, 1/4 . What is the probability in the following cases
i) the problem is solved
ii) Only one of them solves it correctly.
- Five dice are thrown simultaneously . If the occurrence of an even number is considered as a “ success” , find the probability of at most 3 successes BD
- A laboratory blood test is 99% effective in detecting a certain disease when it is in fact present . However the test also yields a false positive result for 0.5%
of the healthy person tested (i.e. if a healthy person is tested then with
probability 0.005, the test will imply that he has the disease. If 0.1 percent of
the population actually has the disease , What is the probability that a person
has the disease given that the test result is positive ? BT
- A pair of dice is thrown 4 times. If getting a doublet is considered a success, find the probability distribution of number of succeses. PDT
- If E and F are independent events prove that E and F’ are independent.
- If a machine is correctly set up, it produces 90% acceptable items. If it is incorrectly set up, it produces only 40% acceptable items. Past experience shows that 80% of the set ups are correctly done. If after a certain set up, the machine produces 2 acceptable items, find the probability that the machine is correctly set up. BT-NOTE THE 2.SEE TEXT BOOK EXAMPLE SUM
- Let x denote a number of collages where you will apply after your results and P( X = x ) denote your probability of getting admission in x number of collage it is given that
(i) Find the value of K
(ii) What is the probability that you will get admission in exactly two collages
(iii) Find the mean & variance of probability distributions.  k is positive constant
- If A and B are independent events then prove that A’ and B’ are also independent events
- From a lot of 30 bulbs which include 6 defectives, a sample of 4 bulbs is drawn at random with replacement. Find the probability distribution of the number of defective bulbs.
- In a test, and examinee either guesses or copies or knows the answer to a multiple
choice question with 4 choices, the probability that he makes a guess is 1/3 and the
probability that he copies the answer is 1/6. the probability that his answer is correct,
given that he copied it is 1/8. Find the probability that he knew the answer to the question. BT
- Two cards are drawn successively with replacement from a well-shuffled pack of 52 cards .find the probability distribution of the number of aces .find its mean and standard deviation.
- In shuffling a pack of 52 playing cards, four are accidentally dropped .find chance that missing cards should be one from each suit.
- If P(A) = 0.2, P(B) = 0.3 and P (A U B ) = 0.4, where a & b are two events associated with a random experiment. Find P (A ∩ B) and P(A / B)
- A bag contains 3 white, 4 red and 5 black balls. Two balls are drawn one after the
other without replacement. Find the probability that of the two drawn balls, one is white
and the other is black.
- Two dice are throw together. What is the probability that the sum of the number on
the two faces is divisible by 3 or 4?
Submitted By Mrs. E.Praveen
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