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RD Sharma - Volume 2

Exercise 31.1

1 2 A 2 B 3 4 5 6 7 8 9

Exercise 31.2

1 2 3 4 5 6 A 6 B 6 C 7 8 9 10 11 12 13 14

Exercise 31.3

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Exercise 31.4

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Exercise 31.5

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Exercise 31.6

1 2 3 4 5 6 7 8 9 10 11 12 13

Exercise 31.7

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Very short answer

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MCQ

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Q. 305.0( 1 Vote )

Fatima and John appear in an interview for two vacancies for the same post. The probability of Fatima’s selection is 1/7 and that of John’s selection is 1/5. What is the probability that

i. Both of them are selected

ii. Only one of them will be selected

iii. None of them will be selected

Class 12th RD Sharma - Volume 2 31. Probability

Answer :

Given that,

⇒ P(F_S) = P(Fatima’s selection)

⇒

⇒ P(F_N) = P(Not selecting Fatima)

⇒

⇒

⇒ P(J_S) = P(John’s selection)

⇒

⇒ P(J_N) = P(Not selecting John)

⇒

⇒

We need to find:

i. Both of them will be selected

ii. Only one of them will be selected

iii. None of them will be selected

⇒ P(S_both) = P(Both of them are selected)

Since selection of each person is an independent event their probabilities multiply each other

⇒

⇒

⇒

⇒ P(S_one) = P(Only one of them is selected)

⇒ P(S_one) = P(only Fatima is selected) + P(only John is selected)

Since selection of each person is an independent event their probabilities multiply each other

⇒

⇒

⇒

⇒ P(S_none) = P(None of them are selected)

Since selection of each person is an independent event their probabilities multiply each other

⇒

⇒

⇒

∴ The required probabilities are .

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PREVIOUSThere are 3 red and 5 black balls in bag ‘A’; and 2 red and 3 black balls in bag ‘B’. One ball is drawn from bag ‘A’ and two from bag ‘B’. Find the probability that out of the 3 balls drawn one is red and 2 are black.NEXTA bag contains 8 marbles of which 3 are blue and 5 are red. One marble is drawn at random, its colour is noted and the marble is replaced in the bag. A marble is again drawn from the bag and its colour is noted. Find the probability that the marble will bei. Blue followed by redii. Blue and red in any orderiii. Of the same colour

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