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Published on: 21/09/2019
Introduction To Probability Theory
Download Tamil Nadu 11th Standard Maths question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.
Questions + Answers key
Take MCQ Maths Test1.
Given that the events A and B are such that P(A) = \(\frac { 1 }{ 2 } \), P(AUB) = \(\frac { 3 }{ 5 } \) and P(B) = p. find P if they are mutually exclusive events.
2.
A die is tossed thrice. find the probability of getting an odd number atleast once?
3.
The probability that student selected at random from a class will pass in Mathematics is \(\frac { 2 }{ 3 } \) and the probability that he passes in Mathematics and English is \(\frac { 1 }{ 3 } \). What is the probability that he will pass in English if it is known that he has passed in Mathematics?
4.
If P(\(\bar { A } \)) = 0.6 P(B) = 0.7 and \(P\left( \frac { B }{ A } \right) =0.4\) , then find \(P\left( \frac { A }{ B } \right) \)and \(P(A\cup B)\)
5.
Given that P(A) =0.52, P(B)=0.43, and P(A∩B)=0.24, find
\(P(\overline { A } \cup \overline { B } )\)
6.
Nine coins are tossed once, find the probability to get at least two heads
7.
A single card is drawn from a pack of 52 cards. What is the probability that
The card is an ace or a king?
8.
If two coins are tossed simultaneously, then find the probability of getting (i) one head and one tail (ii) at most two tails
9.
If an experiment has exactly the three possible mutually exclusive outcomes A, B, and C, check in each case whether the assignment of probability is permissible.
P(A) = 0.421, P(B) = 0.527 P(C) = 0.042
10.
If an experiment has exactly the three possible mutually exclusive outcomes A, B, and C, check in each case whether the assignment of probability is permissible
\(P(A)=\frac { 2 }{ 5 } ,\quad P(B)=\frac { 1 }{ 5 } ,\quad P(C)=\frac { 3 }{ 5 } \)
11.
There are two identical urns containing respectively 6 black and 4 red balls, 2 black and 2 red balls. An urn is chosen at random and a ball is drawn from it.
(i) find the probability that the ball is black
(ii) if the ball is black, what is the probability that it is from the first urn?
12.
Given that P(A) = 0.52, P(B) = 0.43, and P(A∩B) = 0.24, find P\( \left( A\cap \overline { B } \right) \)
13.
A cricket club has 16 members, of whom only 5 can bowl. What is the probability that in a team of 11 members at least 3 bowlers are selected?
14.
A bag contains 7 red and 4 black balls, 3 balls are drawn at random. Find the probability that (i) all are red (ii) one red and 2 black.
15.
Five mangoes and 4 apples are in a box. If two fruits are chosen at random, find the probability that (i) one is a mango and the other is an apple (ii) both are of the same variety.
1.
Since A and B are mutually exclusive, P(A\(\cap \)B) = 0
Now, P(AUB) = P(A) + P(B) - P(A\(\cap \)B)
\(\Rightarrow \frac { 3 }{ 5 } =\frac { 1 }{ 2 } +p-0\)
\(\Rightarrow p=\frac { 3 }{ 5 } -\frac { 1 }{ 2 } =\frac { 6-5 }{ 10 } =\frac { 1 }{ 10 } \)
\(\therefore\) \(p=\frac { 1 }{ 10 } \)
2.
Probability of getting odd number = \(\frac { 3 }{ 6 } =\frac { 1 }{ 2 } \)
Probability of getting even numbers = 1-\(\frac { 1 }{ 2 } =\frac { 1 }{ 2 } \)
Now, probability of getting no odd number when the die is tossed twice = Probability of getting even number when the die is tossed thrice.
\(\Rightarrow \quad \frac { 1 }{ 2 } \times \frac { 1 }{ 2 } \times \frac { 1 }{ 2 } =\frac { 1 }{ 8 } \)
\(\therefore\) P(Odd number atleast once) = \(1-\frac { 1 }{ 8 } =\frac { 7 }{ 8 } \)
3.
Let m be the event the selected student passes in mathematics and E be the event that the selected student passes in English.
\(\therefore P(M)=\frac { 2 }{ 3 } \) and P(M\(\cap \)E)=\(\frac { 1 }{ 3 } \)
\(\therefore P(E/M)=\frac { P(M\cap E) }{ P(M) } =\frac { \frac { 1 }{ 3 } }{ \frac { 2 }{ 3 } } =\frac { 1 }{ 3 } \times \frac { 3 }{ 2 } =\frac { 1 }{ 2 } \)
4.
Given \(P(\bar { A } )=0.6\)
\(\Rightarrow P(A)=1-P(\bar { A } )=1-0.6=0.4\)
P(B) = 0.7 and P(B/A) = 0.4
We know that P(B/A) = \(\frac { P(A\cap B) }{ P(A) } \)
\(\Rightarrow 0.4=\frac { P(A\cap B) }{ 0.4 } \)
\(\Rightarrow P(A\cap B)=0.16\)
Now, P(A/B) = \(\frac { P(A\cap B) }{ P(B) } =\frac { 0.16 }{ 0.7 } =0.2286\)
Also, P(A\(\cup \) B) = P(A) + P(B) - P(A\(\\ \cap \)B)
= 0.4 + 0.7 - 0.16 = 1.1 - 0.16 = 0.94
5.
\(P(\overline { A } \cup \overline { B } )\)=\(\left( \overline { A\cap B } \right) \)(By de Morgan's law)
1-P(A∩B)=1-0.24
=0.76
6.
Let S be the sample space and A be the event of getting at least two heads.
Therefore, the event Ā denotes, getting at most one head.
n(S) = 29 = 512, n(Ā) = 9C0 + 9C1= 1 + 9 = 10
\(P(\bar{A})=\frac{10}{512}=\frac{5}{256} \)
\(
P(A)=1-P(\bar{A})=1-\frac{5}{256}=\frac{251}{256}\)


7.
S = {Pack of 52 cards}
\(\therefore\) n(S) = 52
P(ace card or a king card) = P(ace card) + P(king card)
= \(\frac{4}{52}+\frac{4}{52}=\frac{8}{52}=\frac{2}{13}\)
8.
The sample space is S = {HH, HT, TH, TT}
⇒ n(S) = 4
(i) Let A be the event of getting one head and one tail, then
A = {HT, TH}
n(A) = 2
\(\therefore\) \(P(A)=\frac{n(B)}{n(S)}=\frac{4}{4}=1\)
(ii) Let A be the event of getting atmose two tails, then
\(\therefore\) B = {HH,HT,TH,TT}
\(\therefore\) \(P(B)=\frac{n(B)}{n(S)}=\frac{4}{4}=1\)
9.
since the experiment has exactly the three possible mutually exclusive outcomes A, B and C, they must be exhaustive events.
\(\Rightarrow S=A\cup B\cup C\)
Therefore, by axioms of probability
\(P(A)\ge 0,P(B)\ge P(C)\ge 0\) and
\(P(A\cup B\cup C)=P(A)+P(B)+P(C)=P(S)=1\)
Even though P(A) + P(B) + P(C) = 0.421 + 0.527 + 0.042 = 0.990 < 1
therefore, the assignment is not permissible

10.
Since the experiment has exactly the three possible mutually exclusive outcomes A, B and C, they must be exhaustive events.
\(\Rightarrow S=A\cup B\cup C\)
Therefore, by axioms of probability
\(P(A)\ge 0,P(B)\ge P(C)\ge 0\) and
\(P(A\cup B\cup C)=P(A)+P(B)+P(C)=P(S)=1\)
Given that \(P(A)=\frac { 2 }{ 5 } \ge ,\quad P(B)=\frac { 1 }{ 5 } \ge 0,\quad P(C)=\frac { 3 }{ 5 } \ge 0\)
But \(P(S)=P(A)+P(B)+P(C)=\frac { 2 }{ 5 } +\frac { 1 }{ 5 } +\frac { 6 }{ 5 } >1\)
Therefore the assignment is not permissible

11.
Let A1 be the event of selecting balls from urn I and A2 be the event of selecting urn II.
Let B be the event of a black ball is drawn from it.
Then we have \(P\left(A_1\right)=P\left(A_2\right)=\frac{1}{2}\)
\(P\left(B / A_1\right)=\frac{6 C_1}{10 C_1} ; P\left(B / A_2\right)=\frac{2 C_1}{1 C_1}\)
\(\text {(i) } P(B)=P\left(A_1\right) \cdot P\left(B / A_1\right)+P\left(A_2\right): P\left(B / A_2\right)\)
\(=\frac{1}{2} \cdot \frac{6 C_1}{10 C_1}+\frac{1}{2} \cdot \frac{2 C_1}{4 C_1} \)
\(=\frac{1}{2}\left[\frac{6}{10}+\frac{2}{4}\right]=\frac{1}{2}\left[\frac{3}{5}+\frac{1}{2}\right]=\frac{1}{2}\left[\frac{6+5}{10}\right]\)
\(=\frac{11}{20} \)
(ii) P(I/B)
\(=\frac{P(B/I)P(I)}{P(B)}\)
\(=\frac{\frac{6}{10}\times \frac{1}{2}}{\frac{11}{20}}=\frac{6}{20}/\frac{11}{20}=\frac{6}{11}\)
12.
P\( \left( A\cap \overline { B } \right) \) = P(A) - P(A∩B)
= 0.52 - 0.24 = 0.28
P\( \left( A\cap \overline { B } \right) \) = 0.28
13.
Let A, B, C be the three possible events of selection.
A is 3 bowlers 8 others
B is 4 bowlers 7 others
C is 5 bowlers 6 others
\(P \quad(A t \text { loast } 3 \text { bowlers })=P(A \cup B \cup C) \)
\(=P(A)+P(B)+P(C)\)
\(=\frac{5 C_3 \times 11 C_8}{16 C_{11}}+\frac{5 C_1 \times 11 C_7}{16 C_{11}}+\frac{5 C_5 \times 11 C_6}{16 C_{11}}\)
\(=\frac{5 C_2 \times 11 C_3+5 C_1 \times 11 C_4+1 \times 11 C_5}{16 C_5}\)
\(=\frac{\frac{5 \times 4}{1 \times 2} \times \frac{11 \times 10 \times 9}{1 \times 2 \times 3}+\frac{5 \times 11 \times 10 \times 9 \times 8}{1 \times 2 \times 3 \times 4}}{+\frac{11 \times 10 \times 9 \times 8 \times 7}{1 \times 2 \times 3 \times 4 \times 5}} \)
\(=\frac{16 \times 15 \times 14 \times 13 \times 12}{1 \times 2 \times 3 \times 4 \times 5}\)
\(P(A \cup B \cup C) =\frac{\frac{11 \times 10 \times 9}{2 \times 3}\left[\frac{5 \times 4}{1 \times 2}+\frac{5 \times 8}{4}+\frac{8 \times 7}{4 \times 5}\right]}{2 \times 14 \times 13 \times 12}\)
\(=\frac{11 \times 5 \times 3 \times\left[10+10+\frac{14}{5}\right]}{2 \times 14 \times 13 \times 12} \)
\(=\frac{11 \times 5 \times 3 \times 114}{2 \times 14 \times 13 \times 12 \times 5}\)
\(=\frac{11 \times 57}{14 \times 13 \times 4} \)
\(=\frac{627}{728}
\)
14.
Let A be the event of getting 3 red balls, and B be the evenl of getting onered and 2 black balls, then
\((i) P(A)=\frac{7 C_3}{11 C_3}=\frac{7 \times 6 \times 5}{11 \times 10 \times 9}=\frac{7}{33} \)
\((ii) P(B)=\frac{7 C_1 \times 4 C_2}{11 C_3}=\frac{7 \times \frac{A^2 \times \not p}{1 \times \not 2}}{\frac{11 \times 10^5 \times \phi^2}{1 \times 2 \times} \times \not p}=\frac{14}{55}\)
15.
(i) Let A be the event ofgetting one mango and one apple, Then
\(P(A)=\frac{5 C_1 \times 4 C_1}{9 C_2}=\frac{5}{9}\)
| M | A | T |
| 5 | 4 | 9 |
(ii) Let B and C be the events of getting both are mango and both are an apple respectively then
\(P(\text { Bor } C) =P(B)+P(C) \)
\(=\frac{5 C_2}{9 C_2}+\frac{4 C_2}{9 C_2}=\frac{5 \times 4}{9 \times 8}+\frac{4 \times 3}{9 \times 8} \)
\(=\frac{8}{18}=\frac{4}{9}\)
11th Standard Syllabus & Materials
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