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NCERT solutions Mathematics Class 11 chapter 16 Probability

Chapters

NCERT Mathematics Class 11

Mathematics Textbook for Class 11

Chapter 16 - Probability

Pages 386 - 387

Describe the sample space for the indicated experiment: A coin is tossed three times.

Q 1 | Page 386

Describe the sample space for the indicated experiment: A die is thrown two times.

Q 2 | Page 386

Describe the sample space for the indicated experiment: A coin is tossed four times.

Q 3 | Page 386

Describe the sample space for the indicated experiment: A coin is tossed and a die is thrown.

Q 4 | Page 386

Describe the sample space for the indicated experiment: A coin is tossed and then a die is rolled only in case a head is shown on the coin.

Q 5 | Page 386

2 boys and 2 girls are in Room X, and 1 boy and 3 girls in Room Y. Specify the sample space for the experiment in which a room is selected and then a person.

Q 6 | Page 386

One die of red colour, one of white colour and one of blue colour are placed in a bag. One die is selected at random and rolled, its colour and the number on its uppermost face is noted. Describe the sample space.

Q 7 | Page 386

An experiment consists of recording boy-girl composition of families with 2 children.

(i) What is the sample space if we are interested in knowing whether it is a boy or girl in the order of their births?

(ii) What is the sample space if we are interested in the number of girls in the family?

Q 8 | Page 386

A box contains 1 red and 3 identical white balls. Two balls are drawn at random in succession without replacement. Write the sample space for this experiment.

Q 9 | Page 387

An experiment consists of tossing a coin and then throwing it second time if a head occurs. If a tail occurs on the first toss, then a die is rolled once. Find the sample space.

Q 10 | Page 387

Suppose 3 bulbs are selected at random from a lot. Each bulb is tested and classified as defective (D) or non-defective (N). Write the sample space of this experiment?

Q 11 | Page 387

A coin is tossed. If the out come is a head, a die is thrown. If the die shows up an even number, the die is thrown again. What is the sample space for the experiment?

Q 12 | Page 387

The numbers 1, 2, 3 and 4 are written separately on four slips of paper. The slips are put in a box and mixed thoroughly. A person draws two slips from the box, one after the other, without replacement. Describe the sample space for the experiment.

Q 13 | Page 387

An experiment consists of rolling a die and then tossing a coin once if the number on the die is even. If the number on the die is odd, the coin is tossed twice. Write the sample space for this experiment.

Q 14 | Page 387

A coin is tossed. If it shows a tail, we draw a ball from a box which contains 2 red and 3 black balls. If it shows head, we throw a die. Find the sample space for this experiment.

Q 15 | Page 387

A die is thrown repeatedly until a six comes up. What is the sample space for this experiment?

Q 16 | Page 387

Page 393

A die is rolled. Let E be the event “die shows 4” and F be the event “die shows even number”. Are E and F mutually exclusive?

Q 1 | Page 393

A die is thrown. Describe the following events:

(i) A: a number less than 7

(ii) B: a number greater than 7

(iii) C: a multiple of 3

(iv) D: a number less than 4

(v) E: an even number greater than 4 (vi) F: a number not less than 3

Also find A ∪ B, A ∩ B, B ∪ C, E ∩ F, D  ∩ E, A – C, D – E, E Ç F', F'

Q 2 | Page 393

An experiment involves rolling a pair of dice and recording the numbers that come up. Describe the following events:

A: the sum is greater than 8, B: 2 occurs on either die

C: The sum is at least 7 and a multiple of 3.

Which pairs of these events are mutually exclusive?

Q 3 | Page 393

Three coins are tossed once. Let A denote the event "three heads show", B denote the event "two heads and one tail show". C denote the event "three tails show" and D denote the event "a head shows on the first coin". Which events are

(i) mutually exclusive?

(ii) simple?

(iii) compound?

Q 4 | Page 393

Three coins are tossed. Describe Two events which are mutually exclusive.

Q 5.1 | Page 393

Three coins are tossed. Describe Three events which are mutually exclusive and exhaustive.

Q 5.2 | Page 393

Three coins are tossed. Describe Two events, which are not mutually exclusive.

 

Q 5.3 | Page 393

Three coins are tossed. Describe Two events which are mutually exclusive but not exhaustive.

Q 5.4 | Page 393

Three coins are tossed. Describe Three events which are mutually exclusive but not exhaustive.

Q 5.5 | Page 393

Two dice are thrown. The events A, B and C are as follows:

A: getting an even number on the first die.

B: getting an odd number on the first die.

C: getting the sum of the numbers on the dice ≤ 5

Describe the events

(i) A' 

(ii) not B

(iii) A or B

(iv) A and B

(v) A but not C

(vi) B or C

(vii) B and C

(viii) A ∩ B' ∩ C'

Q 6 | Page 393

Refer to question 6 above, state true or false: (give reason for your answer)
(i) A and B are mutually exclusive

Q 7.1 | Page 393

Two dice are thrown. The events A, B and C are as follows:

A: getting an even number on the first die.

B: getting an odd number on the first die.

C: getting the sum of the numbers on the dice ≤ 5

State true or false: (give reason for your answer)

A and B are mutually exclusive and exhaustive

Q 7.2 | Page 393

Two dice are thrown. The events A, B and C are as follows:

A: getting an even number on the first die.

B: getting an odd number on the first die.

C: getting the sum of the numbers on the dice ≤ 5

State true or false: (give reason for your answer)'

A = B'

Q 7.3 | Page 393

Two dice are thrown. The events A, B and C are as follows:

A: getting an even number on the first die.

B: getting an odd number on the first die.

C: getting the sum of the numbers on the dice ≤ 5

State true or false: (give reason for your answer)

 A and C are mutually exclusive

Q 7.4 | Page 393

Two dice are thrown. The events A, B and C are as follows:

A: getting an even number on the first die.

B: getting an odd number on the first die.

C: getting the sum of the numbers on the dice ≤ 5

State true or false: (give reason for your answer)

A and B' are mutually exclusive

Q 7.5 | Page 393

Two dice are thrown. The events A, B and C are as follows:

A: getting an even number on the first die.

B: getting an odd number on the first die.

C: getting the sum of the numbers on the dice ≤ 5

State true or false: (give reason for your answer)

A' , B' ,C are mutually exclusive and exhaustive.

Q 7.6 | Page 393

Pages 403 - 406

Which of the following can not be valid assignment of probabilities for outcomes of sample space S = {ω1, ω2,ω3,ω4,ω5,ω6,ω7}

Assignment

ω1

ω2

ω3

ω4

ω5

ω6

ω7

(a)

0.1

0.01

0.05

0.03

0.01

0.2

0.6

(b)

1/7

1/7

1/7

1/7

1/7

1/7

1/7

(c)

0.1

0.2

0.3

0.4

0.5

0.6

0.7

(d)

–0.1

0.2

0.3

0.4

–0.2

0.1

0.3

(e)

1/14

2/14

3/14

4/14

5/14

6/14

15/14

Q 1 | Page 403

A coin is tossed twice, what is the probability that at least one tail occurs?

Q 2 | Page 404

A die is thrown, find the probability of following events:

(i) A prime number will appear,

(ii) A number greater than or equal to 3 will appear,

(iii) A number less than or equal to one will appear,

(iv) A number more than 6 will appear,

(v) A number less than 6 will appear.

Q 3 | Page 404

A card is selected from a pack of 52 cards.

(a) How many points are there in the sample space?

(b) Calculate the probability that the card is an ace of spades.

(c) Calculate the probability that the card is (i) an ace (ii) black card.

Q 4 | Page 404

A fair coin with 1 marked on one face and 6 on the other and a fair die are both tossed. Find the probability that the sum of numbers that turn up is (i) 3 (ii) 12

Q 5 | Page 404

There are four men and six women on the city council. If one council member is selected for a committee at random, how likely is it that it is a woman?

Q 6 | Page 404

A fair coin is tossed four times, and a person win Re 1 for each head and lose Rs 1.50 for each tail that turns up. From the sample space calculate how many different amounts of money you can have after four tosses and the probability of having each of these amounts.

Q 7 | Page 404

Three coins are tossed once. Find the probability of getting

(i) 3 heads

(ii) 2 heads

(iii) at least 2 heads

(iv) at most 2 heads

(v) no head

(vi) 3 tails

(vii) exactly two tails

(viii) no tail (ix) at most two tails.

Q 8 | Page 404

If 2/11 is the probability of an event, what is the probability of the event ‘not A’.

Q 9 | Page 404

A letter is chosen at random from the word ‘ASSASSINATION’. Find the probability that letter is (i) a vowel (ii) an consonant

Q 10 | Page 404

In a lottery, person choses six different natural numbers at random from 1 to 20, and if these six numbers match with the six numbers already fixed by the lottery committee, he wins the prize. What is the probability of winning the prize in the game? [Hint: order of the numbers is not important.]

Q 11 | Page 405

Check whether the following probabilities P(A) and P(B) are consistently defined

P(A) = 0.5, P(B) = 0.7, P(A ∩ B) = 0.6

Q 12.1 | Page 405

Check whether the following probabilities P(A) and P(B) are consistently defined'

P(A) = 0.5, P(B) = 0.4, P(A ∪ B) = 0.8

Q 12.2 | Page 405

Fill in the blanks in following table:

 

P(A)

P(B)

P(A  B)

P(A  B)

 

1/3

1/5

1/15

Q 13.1 | Page 405

Fill in the blanks in following table:

 

P(A)

P(B)

P(A  B)

P(A  B)

 

0.35

0.25

0.6

 

Q 13.2 | Page 405

Fill in the blanks in following table:

 

P(A)

P(B)

P(A  B)

P(A  B)

 

0.5

0.35

0.7

Q 13.3 | Page 405

Given P(A) = 3/5 and P(B) = 1/5 . Find P(A or B), if A and B are mutually exclusive events.

Q 14 | Page 405

If E and F are events such that P(E) =1/4 , P(F) =1/2  and P(E and F) =1/8, find:(i) P(E or F), (ii) P(not E and not F).

Q 15 | Page 405

Events E and F are such that P(not E or not F) = 0.25, State whether E and F are mutually exclusive.

 
Q 16 | Page 405

A and B are events such that P(A) = 0.42, P(B) = 0.48 and P(A and B) = 0.16. Determine P(not A)

Q 17.1 | Page 405

A and B are events such that P(A) = 0.42, P(B) = 0.48 and P(A and B) = 0.16. Determine  P (not B)

Q 17.2 | Page 405

A and B are events such that P(A) = 0.42, P(B) = 0.48 and P(A and B) = 0.16. Determine P(A or B).

Q 17.3 | Page 405

In Class XI of a school 40% of the students study Mathematics and 30% study Biology. 10% of the class study both Mathematics and Biology. If a student is selected at random from the class, find the probability that he will be studying Mathematics or Biology.

Q 18 | Page 405

In an entrance test that is graded on the basis of two examinations, the probability of a randomly chosen student passing the first examination is 0.8 and the probability of passing the second examination is 0.7. The probability of passing at least one of them is 0.95. What is the probability of passing both?

Q 19 | Page 405

The probability that a student will pass the final examination in both English and Hindi is 0.5 and the probability of passing neither is 0.1. If the probability of passing the English examination is 0.75, what is the probability of passing the Hindi examination?

Q 20 | Page 405

In a class of 60 students, 30 opted for NCC, 32 opted for NSS and 24 opted for both NCC and NSS. If one of these students is selected at random, find the probability that

(i) The student opted for NCC or NSS.

(ii) The student has opted neither NCC nor NSS.

(iii) The student has opted NSS but not NCC.

Q 21 | Page 406

Pages 408 - 409

A box contains 10 red marbles, 20 blue marbles and 30 green marbles. 5 marbles are drawn from the box, what is the probability that

(i) all will be blue?

(ii) atleast one will be green?

Q 1 | Page 408

4 cards are drawn from a well-shuffled deck of 52 cards. What is the probability of obtaining 3 diamonds and one spade?

Q 2 | Page 408

A die has two faces each with number ‘1’, three faces each with number ‘2’ and one face with number ‘3’. If die is rolled once, determine

(i) P(2)

(ii) P(1 or 3)

(iii) P(not 3)

Q 3 | Page 409

In a certain lottery, 10,000 tickets are sold and ten equal prizes are awarded. What is the probability of not getting a prize if you buy (a) one ticket (b) two tickets (c) 10 tickets?

Q 4 | Page 409

Out of 100 students, two sections of 40 and 60 are formed. If you and your friend are among the 100 students, what is the probability that

(a) you both enter the same sections?

(b) you both enter the different sections?

Q 5 | Page 409

Three letters are dictated to three persons and an envelope is addressed to each of them, the letters are inserted into the envelopes at random so that each envelope contains exactly one letter. Find the probability that at least one letter is in its proper envelope

Q 6 | Page 409

A and B are two events such that P(A) = 0.54, P(B) = 0.69 and P(A ∩ B) = 0.35.

Find

(i) P(A ∩ B)

(ii) P(A′ ∩ B′)

(iii) P(A ∩ B′) (iv) P(B ∩ A′)

Q 7 | Page 409

From the employees of a company, 5 persons are selected to represent them in the managing committee of the company. Particulars of five persons are as follows:

S. No.

Name

Sex

Age in years

1.

Harish

M

30

2.

Rohan

M

33

3.

Sheetal

F

46

4.

Alis

F

28

5.

Salim

M

41

A person is selected at random from this group to act as a spokesperson. What is the probability that the spokesperson will be either male or over 35 years?

Q 8 | Page 409

If 4-digit numbers greater than 5,000 are randomly formed from the digits 0, 1, 3, 5, and 7, what is the probability of forming a number divisible by 5 when, (i) the digits are repeated? (ii) the repetition of digits is not allowed?

Q 9 | Page 409

The number lock of a suitcase has 4 wheels, each labelled with ten digits i.e., from 0 to 9. The lock opens with a sequence of four digits with no repeats. What is the probability of a person getting the right sequence to open the suitcase?

Q 10 | Page 409

NCERT Mathematics Class 11

Mathematics Textbook for Class 11
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