Mathematical and Logical Reasoning — NCERT Solutions
CBSE · Class 11 · Applied Mathematics
NCERT Solutions for Mathematical and Logical Reasoning, CBSE Class 11 Applied Mathematics: 23 textbook questions solved step by step.
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Check your Progress-1
1Check whether the following sentence is a statement. Give reason for your answer.
8 is less than 6.Show solution
Given sentence: "8 is less than 6."
Concept: A sentence is a mathematically acceptable statement if it is either true or false (but not both).
Working: The sentence "8 is less than 6" is false because . Since it has a definite truth value (false), it qualifies as a statement.
Conclusion: Yes, it is a statement (a false statement).
2Check whether the following sentence is a statement. Give reason for your answer.
Every set is a finite set.Show solution
Given sentence: "Every set is a finite set."
Concept: A sentence is a statement if it is either true or false.
Working: The sentence is false because there exist sets that are not finite (e.g., the set of natural numbers is infinite). Since it has a definite truth value (false), it qualifies as a statement.
Conclusion: Yes, it is a statement (a false statement).
3Check whether the following sentence is a statement. Give reason for your answer.
The sun is a star.Show solution
Given sentence: "The sun is a star."
Concept: A sentence is a statement if it is either true or false.
Working: It is a scientifically established fact that the Sun is a star. Therefore, this sentence is always true and has a definite truth value.
Conclusion: Yes, it is a statement (a true statement).
4Check whether the following sentence is a statement. Give reason for your answer.
Mathematics is fun.Show solution
Given sentence: "Mathematics is fun."
Concept: A sentence is a statement only if it is either definitely true or definitely false.
Working: This sentence is subjective — for those who enjoy mathematics it may be true, but for others it may not be. It does not have a definite, universal truth value.
Conclusion: No, it is NOT a statement because its truth value varies from person to person.
5Check whether the following sentence is a statement. Give reason for your answer.
There is no rain without clouds.Show solution
Given sentence: "There is no rain without clouds."
Concept: A sentence is a statement if it is either true or false.
Working: This is a scientifically true fact — rain requires clouds. The sentence has a definite truth value (true).
Conclusion: Yes, it is a statement (a true statement).
6Check whether the following sentence is a statement. Give reason for your answer.
How far is Chennai from here?Show solution
Given sentence: "How far is Chennai from here?"
Concept: Questions, exclamations, and commands are not statements because they cannot be assigned a truth value of true or false.
Working: This is an interrogative sentence (a question). It does not assert anything and cannot be said to be true or false.
Conclusion: No, it is NOT a statement because it is a question and does not have a truth value.
Check your Progress-2
1For the following statement, determine whether an inclusive "Or" or exclusive "Or" is used. Give reason for your answer.
The school is closed if it is a holiday or a Sunday.Show solution
Given statement: "The school is closed if it is a holiday or a Sunday."
Concept:
- Inclusive 'Or': At least one of the two conditions is true (both can be true simultaneously).
- Exclusive 'Or': Exactly one of the two conditions is true (both cannot be true simultaneously).
Working: A day can be both a holiday AND a Sunday at the same time (e.g., a national holiday falling on a Sunday). In either case or both cases, the school remains closed. So both conditions can hold simultaneously.
Conclusion: The "Or" used here is Inclusive Or, because the school is closed when it is a holiday, or a Sunday, or both.
2For the following statement, determine whether an inclusive "Or" or exclusive "Or" is used. Give reason for your answer.
Two lines intersect at a point or are parallel.Show solution
Given statement: "Two lines intersect at a point or are parallel."
Concept: Exclusive 'Or' means exactly one of the two alternatives holds; both cannot be true simultaneously.
Working: Two lines in a plane cannot intersect at a point AND be parallel at the same time. These are mutually exclusive situations — if two lines intersect, they are not parallel, and if they are parallel, they do not intersect.
Conclusion: The "Or" used here is Exclusive Or, because both conditions cannot be true simultaneously.
3For the following statement, determine whether an inclusive "Or" or exclusive "Or" is used. Give reason for your answer.
Students can take French or Sanskrit as their third language.Show solution
Given statement: "Students can take French or Sanskrit as their third language."
Concept: Exclusive 'Or' means exactly one of the two alternatives holds.
Working: A student can choose only one language as their third language — either French or Sanskrit, but not both at the same time. The two choices are mutually exclusive.
Conclusion: The "Or" used here is Exclusive Or, because a student cannot take both French and Sanskrit simultaneously as their third language.
Check your Progress-3
1Statements:
(I) Some actors are singers.
(II) All the singers are dancers.
Conclusions:
(1) Some actors are dancers.
(2) No singer is actor.
Give answer: (A) If only conclusion (1) follows. (B) If only conclusion (2) follows. (C) If either (1) or (2) follows. (D) If neither (1) nor (2) follows. (E) If both (1) and (2) follow.Show solution
Given Statements:
- Some actors are singers. (partial overlap between actors and singers)
- All singers are dancers. (singers ⊂ dancers)
Analysis of Conclusion (1): "Some actors are dancers."
Since some actors are singers, and all singers are dancers, those actors who are singers must also be dancers. Therefore, some actors are dancers. ✓ Conclusion (1) follows.
Analysis of Conclusion (2): "No singer is actor."
Statement I says "Some actors are singers," which directly means some singers ARE actors. So the claim "No singer is actor" is contradicted by Statement I. ✗ Conclusion (2) does not follow.
Answer: (A) — Only conclusion (1) follows.
2Statements:
(I) All the harmoniums are instruments.
(II) All the instruments are flutes.
Conclusions:
(1) All the flutes are instruments.
(2) All the harmoniums are flutes.
Give answer: (A) If only conclusion (1) follows. (B) If only conclusion (2) follows. (C) If either (1) or (2) follows. (D) If neither (1) nor (2) follows. (E) If both (1) and (2) follow.Show solution
Given Statements:
- All harmoniums are instruments. (harmoniums ⊂ instruments)
- All instruments are flutes. (instruments ⊂ flutes)
Analysis of Conclusion (1): "All the flutes are instruments."
Statement II says all instruments are flutes, i.e., instruments ⊂ flutes. This does NOT mean all flutes are instruments (the converse is not necessarily true). ✗ Conclusion (1) does not follow.
Analysis of Conclusion (2): "All the harmoniums are flutes."
Since all harmoniums are instruments (Statement I) and all instruments are flutes (Statement II), by transitivity: all harmoniums are flutes. ✓ Conclusion (2) follows.
Answer: (B) — Only conclusion (2) follows.
3Statements:
(I) Some mangoes are yellow.
(II) Some fruits are mangoes.
Conclusions:
(1) Some mangoes are green.
(2) Fruits are yellow.
Give answer: (A) If only conclusion (1) follows. (B) If only conclusion (2) follows. (C) If either (1) or (2) follows. (D) If neither (1) nor (2) follows. (E) If both (1) and (2) follow.Show solution
Given Statements:
- Some mangoes are yellow.
- Some fruits are mangoes.
Analysis of Conclusion (1): "Some mangoes are green."
The statements only tell us that some mangoes are yellow. Nothing is said about mangoes being green. This cannot be concluded from the given statements. ✗ Conclusion (1) does not follow.
Analysis of Conclusion (2): "Fruits are yellow."
Statement II says only SOME fruits are mangoes, and Statement I says only SOME mangoes are yellow. We cannot conclude that all fruits are yellow. ✗ Conclusion (2) does not follow.
Answer: (D) — Neither conclusion (1) nor conclusion (2) follows.
(I) Some ants are parrots.
(II) All the parrots are apples.
Conclusions:
(1) All the apples are parrots.
(2) Some ants are apples.
Give answer: (A) If only conclusion (1) follows. (B) If only conclusion (2) follows. (C) If either (1) or (2) follows. (D) If neither (1) nor (2) follows. (E) If both (1) and (2) follow.
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Check your Progress-4
a) NPPQ
b) SPPN
c) PPON
d) NQQP
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a) 32987
b) 32897
c) 38987
d) 21987
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'hi mi si' means 'Air is life'.
'si ni zi' means 'Balloon of Air'.
'ci zi mi' means 'Life of PI'.
Which of the following represents 'PI' in that language?
a) hi
b) mi
c) ci
d) si
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321 means 'Glass of Tea'.
426 means 'Tea is Brown'.
796 means 'Trunks are Brown'.
Which of the following represents 'is' in that language?
a) 6
b) 7
c) 4
d) 2
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Check your Progress-5
a) Cousin
b) Sister-in-law
c) Mother
d) Mother-in-law
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a) Grandfather
b) Grandmother
c) Daughter
d) Granddaughter
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a) L+M/N−O
b) L−M×O/P
c) N/M×L/O
d) M+L/O×N
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Check your Progress-6
a. Insurance
b. Provident Fund
c. Salary
d. Shares
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a. 21
b. 17
c. 14
d. 3
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Sources & Official References
- NCERT Official — ncert.nic.in
- CBSE Academic — cbseacademic.nic.in
- CBSE Official — cbse.gov.in
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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