Class 11- Applied Mathematics-NCERT Handbook Solutions-Chapter-3

Chapter 3 Solutions - Mathematical Logic

Check Your Progress 3.1

1. Find the odd man out from the given alternatives.

a. Insurance   b. Provident Fund   c. Salary   d. Shares

Solution: c. Salary

Reasoning: Insurance, Provident Fund, and Shares are all forms of investments or savings vehicles where money is parked for future returns or security. Salary, on the other hand, is a regular form of direct income or remuneration.

2. Which number is odd man out among 3, 5, 11, 14, 17, 21

a. 21   b. 17   c. 14   d. 3

Solution: c. 14

Reasoning: Among the given numbers (3,5,11,14,17,21), 14 is the only even number. All other numbers are odd.

3. Find the odd man out from the figures given below.

a   b   c   d

Solution: c

Note: The figures are not provided in the text, but based on the answer key, figure (c) deviates from the standard pattern established by figures (a), (b), and (d).

Check Your Progress 3.2

1. Statements: Some actors are singers. All the singers are dancers.

Conclusions: I. Some actors are dancers. II. No singer is actor.

Solution: (A) Only conclusion (I) follows.

Reasoning:

  • Since "All singers are dancers", the circle for Singers is entirely inside Dancers.
  • "Some actors are singers" means the Actors circle intersects the Singers circle.
  • Because Actors intersects Singers, and Singers is completely inside Dancers, Actors must necessarily intersect Dancers. Thus, Conclusion I ("Some actors are dancers") is absolutely true.
  • Conclusion II ("No singer is actor") contradicts the first statement directly. Thus, it is false.
Dancers Singers Actors

2. Statements: All the harmoniums are instruments. All the instruments are flutes.

Conclusions: I. All the flutes are instruments. II. All the harmoniums are flutes.

Solution: (B) Only conclusion (II) follows.

Reasoning:

  • "All harmoniums are instruments" means Harmoniums (H) is inside Instruments (I).
  • "All instruments are flutes" means Instruments (I) is inside Flutes (F).
  • Conclusion I ("All the flutes are instruments") is false because Flutes is the outer circle, and there may be flutes that are not instruments.
  • Conclusion II ("All the harmoniums are flutes") is true because H is inside I, and I is inside F, making H completely inside F.
Flutes Instruments Harmoniums

3. Statements: Some mangoes are yellow. Some fruits are mangoes.

Conclusions: I. Some mangoes are green. II. Fruits are yellow.

Solution: (D) Neither (I) nor (II) follows.

Reasoning:

  • Conclusion I ("Some mangoes are green") introduces a new term "green" which is not mentioned in the premises. We cannot logically deduce this.
  • Conclusion II ("Fruits are yellow") implies all fruits are yellow. The premises only state that some mangoes are yellow and some fruits are mangoes. We cannot establish a definite relationship between all fruits and the color yellow.
Fruits Mangoes Yellow

4. Statements: Some ants are parrots. All the parrots are apples.

Conclusions: I. All the apples are parrots. II. Some ants are apples.

Solution: (B) Only conclusion (II) follows.

Reasoning:

  • "All parrots are apples" places the Parrots circle entirely inside the Apples circle.
  • "Some ants are parrots" means the Ants circle intersects the Parrots circle.
  • Since Ants intersects Parrots, and Parrots is inside Apples, Ants MUST also intersect Apples. Thus, Conclusion II ("Some ants are apples") is definitely true.
  • Conclusion I ("All the apples are parrots") is false because Apples is the larger enclosing set; not all apples have to be parrots.
Apples Parrots Ants

Check Your Progress 3.3

1. Pointing to a picture the man said, "The lady in the picture is my nephew's maternal grandmother." How is the lady in the picture related to the man's sister who has no other sister?

(a) Cousin   (b) Sister-in-law   (c) Mother   (d) Mother-in law

Solution: (c) Mother

Reasoning:

1. The man's sister "has no other sister", meaning she is the only sister of the man.

2. The man's "nephew" is the son of this sister.

3. The nephew's "maternal grandmother" is the mother of the nephew's mother.

4. Since the nephew's mother is the man's sister, the maternal grandmother is the mother of the man's sister.

Therefore, the lady in the picture is the Mother of the man's sister.

Lady (F) Married Father (M) Man (M) Only Son Sister (F) Nephew (M)

2. Meenakshi is Kirti's sister. Kaavya is Kirti's mother. Dipesh is Kaavya's father. Esha is Dipesh's mother. Then, how is Meenakshi related to Dipesh?

3. Dipesh is Kaavya's father. This makes Dipesh the maternal grandfather of both Kirti and Meenakshi.

Therefore, Meenakshi is the Granddaughter of Dipesh.

Esha (F) Dipesh (M) Kaavya (F) Meenakshi (F) Kirti (F)

3. P + Q means P is the brother of Q, R - S means R is the father of S, S / T means S is the sister of T, T x U means T is the mother of U. Which of the following means that O is the mother of N?

(a) L + M / N - O   (b) L - M x O / P   (c) N / M x L / O   (d) M + L / O x N

Solution: (d) M + L / O x N

Reasoning: We need to find the expression where O is the mother of N.

According to the given rules, O×N directly translates to "O is the mother of N".

Looking at option (d): M+L/O×N

  • M+L → M is the brother of L
  • L/O → L is the sister of O
  • O×N → O is the mother of N

The last part of the expression definitively establishes that O is the mother of N.

M (M) + L (F) / O (F) x N

Check Your Progress 3.4

1. In a certain language, if CAMEL is coded as DBNFM then how will ROOM be coded?

(a) NPPQ   (b) SPPN   (c) PPON   (d) NQQP

Solution: (b) SPPN

Pattern: Each letter in the word is shifted forward by 1 position in the English alphabet.

C → D, A → B, M → N, E → F, L → M

Applying the same to ROOM:

R → S, O → P, O → P, M → N. The code is SPPN.

2. If BLEPIN is coded as 987416, MATPIN is coded as 123416, then TABLE is coded as?

(a) 32987   (b) 32897   (c) 38987   (d) 21987

Solution: (a) 32987

Pattern: Direct letter-to-number substitution mapping based on the given words.

From BLEPIN = 987416, we get: B=9, L=8, E=7, P=4, I=1, N=6

From MATPIN = 123416, we get: M=1 (Wait, M is another number, let's look closer. Actually MATPIN=123416 and BLEPIN=987416 share PIN=416. M=1, A=2, T=3.)

Let's map TABLE:

  • T = 3
  • A = 2
  • B = 9
  • L = 8
  • E = 7

Combining these gives 32987.

3. In a certain language, 'hi misi' means 'Air is life'. 'sinizi' means 'Balloon of Air'. 'cizimi' means 'Life of Pl'. Which of the following represents 'Pl' in that language?

(a) hi   (b) mi   (c) ci   (d) si

Solution: (c) ci

Reasoning:

1. "hi mi si" = Air is life. "si ni zi" = Balloon of Air. Common word is "Air", common code is "si". So, Air = si.

2. "hi mi si" = Air is life. "ci zi mi" = Life of Pl. Common word is "life", common code is "mi". So, life = mi.

3. "si ni zi" = Balloon of Air. "ci zi mi" = Life of Pl. Common word is "of", common code is "zi". So, of = zi.

4. In "ci zi mi" = Life of Pl, we know life = mi and of = zi. Therefore, the remaining word "Pl" must be the remaining code ci.

4. In a certain language, 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

Solution: (c) 4

Reasoning:

1. 321 = Glass of Tea. 426 = Tea is Brown. Common word is "Tea", common digit is 2. So, Tea = 2.

2. 426 = Tea is Brown. 796 = Trunks are Brown. Common word is "Brown", common digit is 6. So, Brown = 6.

3. In 426 = Tea is Brown, we know Tea = 2 and Brown = 6. The remaining word is "is", which corresponds to the remaining digit 4.

Practice Exercise

Odd Man Out

1. Find the odd man out:
(a) 5720   (b) 6710   (c) 2640   (d) 4270

Solution: (d) 4270

Reasoning: Let's check the divisibility by 11 (difference between sum of alternating digits):

  • 5720: (5+2)-(7+0)=7-7=0 (Divisible by 11)
  • 6710: (6+1)-(7+0)=7-7=0 (Divisible by 11)
  • 2640: (2+4)-(6+0)=6-6=0 (Divisible by 11)
  • 4270: (4+7)-(2+0)=11-2=9 (Not divisible by 11)

2. Find the odd man out:
(a) PQXZ   (b) CQBN   (c) ABDF   (d) PRMN

Solution: (c) ABDF

Reasoning: The first two letters in ABDF are consecutive (A, B). The others do not have the first two letters as consecutive alphabets. (Note: This relies on the standard pattern analysis for odd-one-out exercises).

3. Find the odd man out:
(a) ABYZ   (b) CDWX   (c) EFUV   (d) GHTV

Solution: (d) GHTV

Reasoning: The pattern is taking a pair of consecutive letters from the start of the alphabet, and pairing it with consecutive letters from the end of the alphabet in reverse order.

  • AB paired with YZ (Last two are Z, Y reversed)
  • CD paired with WX (X, W reversed)
  • EF paired with UV (V, U reversed)
  • Following this, GH should be paired with ST. Instead, it is paired with TV. Hence, GHTV is the odd one.

4. Find the odd man out:
(a) 16-18   (b) 56-63   (c) 96-108   (d) 86-99

Solution: (d) 86-99

Reasoning: The ratio of the two numbers in the first three pairs is 8:9.

  • 1618=89
  • 5663=89
  • 96108=89
  • 869989

5. Find the odd man out:
(a) Bird   (b) Kite   (c) Crow   (d) Sparrow

Solution: (a) Bird

Reasoning: Kite, Crow, and Sparrow are specific types of birds. "Bird" is the general class/category to which the others belong.

6. Find the odd man out:
(a) Bangalore   (b) Nagpur   (c) Bhopal   (d) Ranchi

Solution: (b) Nagpur

Reasoning: Bangalore (Karnataka), Bhopal (Madhya Pradesh), and Ranchi (Jharkhand) are all capital cities of Indian states. Nagpur is a major city in Maharashtra but not its capital.

Syllogism

7. Statements:
All pencils are sticks.
Some sticks are boxes.
Conclusions:
I. Some boxes are pencils.
II. All pencils are boxes.

Solution: (d) If neither (I) nor (II) follows.

Reasoning: All pencils are inside the sticks circle. Boxes intersect with the sticks circle. However, there is no definite information that the boxes circle intersects with the pencils circle. Thus, "Some boxes are pencils" is a possibility but not a definite conclusion. "All pencils are boxes" is also not definite.

Sticks Pencils Boxes

8. Statements:
All doctors are humans.
Some humans are teachers.
Conclusions:
I. Some doctors can be teachers.
II. Some teachers are doctors.

Solution: (a) If only conclusion (I) follows.

Reasoning: Conclusion I uses the phrase "can be," denoting a possibility. Since it is possible for the doctor circle and teacher circle to intersect inside the human circle, Conclusion I is true. Conclusion II is a definite statement ("are"), which we cannot guarantee. Hence, only I follows.

Humans Doctors Teachers

9. Statements:
Some fruits are sweets.
All sweets are tasty.
Conclusions:
I. Some fruits are tasty.
II. All fruits are tasty.

Solution: (a) If only conclusion (I) follows.

Reasoning: The "sweets" circle is entirely inside the "tasty" circle. The "fruits" circle intersects the "sweets" circle. Therefore, the part of the fruits circle that is inside the sweets circle must also be inside the tasty circle. Thus, Conclusion I is definitely true. Conclusion II is false because only "some" fruits are known to be tasty.

Tasty Sweets Fruits

10. Statements:
No bird is a mammal.
All mammals are animals.
Conclusions:
I. No bird is an animal.
II. No mammal is a bird.

Solution: (b) If only conclusion (II) follows.

Reasoning: "No bird is a mammal" directly translates to "No mammal is a bird" (conversion is always true for "no"). Hence, Conclusion II is true. Conclusion I is false because birds can still be animals even if they aren't mammals (the "animals" circle can enclose the "bird" circle without touching "mammals").

Animals Mammals Birds NO

11. Statements:
All books are papers.
Some papers are files.
Conclusions:
I. Some files are books.
II. Some papers are books.

Solution: (b) If only conclusion (II) follows.

Reasoning: Since "All books are papers", it naturally follows that the papers circle encompasses the books circle, making "Some papers are books" a definite truth (Conclusion II). Conclusion I cannot be guaranteed because the files circle might intersect the papers circle without touching the books circle.

Papers Books Files

12. Statements:
No pen is a marker.
Some markers are erasers.
Conclusions:
I. Some erasers are pens.
II. No pen is an eraser.

Solution: (d) If neither (I) nor (II) follows.

Reasoning: The relationship between pens and erasers is not defined. Pens and erasers might be completely separate, or they might intersect. Thus, neither a definite positive ("Some erasers are pens") nor a definite negative ("No pen is an eraser") can be concluded for sure.

Pens Markers Erasers NO

Blood Relations

13. Introducing a woman, a man said, "Her husband is the only son of my father". How is that woman related to the man?
(a) Husband   (b) Sister   (c) Wife   (d) Grandson

Solution: (c) Wife

Reasoning: "The only son of my father" refers to the man himself. Therefore, the statement simplifies to "Her husband is me." This makes the woman the wife of the man.

14. R is the son of A's father's sister. S is son of D, who is the mother of G and grandmother of A. H is the father of T and grandfather of R. D is wife of H. How is R related to D?
(a) Nephew   (b) Son   (c) Grandson   (d) Brother

Solution: (c) Grandson

Reasoning:

  1. R is the son of A's father's sister. Let A's father be F, and his sister be aunt F_s. R is the son of F_s.
  2. D is the grandmother of A. This means D is the mother of A's father (F) and his sister (F_s).
  3. Since R is the son of F_s, and D is the mother of F_s, D is the grandmother of R.

Thus, R is the Grandson of D.

15. If 'A#B' means A is father of B, 'A*B' means A is brother of B, 'A@B' means A is mother of B then which of the following is correct about G@T#P?
(a) G is mother of P   (b) P is father of T   (c) T is son of G   (d) P is brother of T

Solution: (c) T is son of G

Reasoning: Analyzing the expression G@T#P:

  • G @ T → G is the mother of T.
  • T # P → T is the father of P.

From "G is the mother of T and T is the father of P," we know T is male. Hence, T is the son of G, making option (c) correct.

G (F) @ (Mother) T (M) # (Father) P

14. R is the son of A's father's sister. S is son of D, who is the mother of G and grandmother of A. H is the father of T and grandfather of R. D is wife of H. How is R related to D?
(a) Nephew   (b) Son   (c) Grandson   (d) Brother

Solution: (c) Grandson

Reasoning:

  1. R is the son of A's father's sister. Let A's father be F, and his sister be aunt F_s. R is the son of F_s.
  2. D is the grandmother of A. This means D is the mother of A's father (F) and his sister (F_s).
  3. Since R is the son of F_s, and D is the mother of F_s, D is the grandmother of R.

Thus, R is the Grandson of D.

H (M) D (F) A's Dad (M) Aunt (F) G S (M) T A R (M)

15. If 'A#B' means A is father of B, 'A*B' means A is brother of B, 'A@B' means A is mother of B then which of the following is correct about G@T#P?
(a) G is mother of P   (b) P is father of T   (c) T is son of G   (d) P is brother of T

Solution: (c) T is son of G

Reasoning: Analyzing the expression G@T#P:

  • G @ T → G is the mother of T.
  • T # P → T is the father of P.

From "G is the mother of T and T is the father of P," we know T is male. Hence, T is the son of G, making option (c) correct.

G (F) @ (Mother) T (M) # (Father) P

16. A, B, C, D, E, F and G are members of a family consisting of four adults and three children, two of whom, F and G are boys. A and D are brothers and A is an engineer. E is a doctor married to one of the brothers and has two children. B is married to D and G is their child. Who is C?
(a) G's Father   (b) F's Father   (c) E's daughter   (d) A's son

Solution: (c) E's daughter

Reasoning:

  • A and D are brothers. B is married to D. So, the couples are (D and B) and (A and E).
  • E is married to A and has two children. D and B have one child, G (who is a boy).
  • Total children = 3 (F, G, and one more). F and G are boys. This means the third child is a girl.
  • Since D and B have child G, A and E must have the remaining two children: F (boy) and C (the only remaining family member).
  • Therefore, C is the daughter of A and E.
A (M, Eng) E (F, Doc) D (M) B (F) Brothers F (M) C (F) G (M)

17. Pointing towards a person a man said to woman, "His father is the son of my mother's only son". How is the man related to that person?
(a) Brother   (b) Father   (c) Son   (d) Grandfather

Solution: (d) Grandfather

Reasoning: "My mother's only son" refers to the man speaking. Therefore, the phrase "son of my mother's only son" means the man's own son. The statement then translates to: "His father is my son." Since the person's father is the speaker's son, the speaker (the man) is the Grandfather of the person.

Mother (F) Only Son Man (M) Son (M) Father of Person

18. A and B are brothers. M is the father of A and brother of S. F is sister of B and K is mother of S. What is the relationship between B and K?
(a) Sister and Brother   (b) Grandson and Grandmother   (c) Nephew and Aunt   (d) Mother and Son

Solution: (b) Grandson and Grandmother

Reasoning:

  • M is the father of A, and since A and B are brothers, M is also the father of B.
  • M is the brother of S.
  • K is the mother of S. Since M and S are siblings, K is also the mother of M.
  • Since K is the mother of M, and M is the father of B, K is the grandmother of B.

Thus, the relationship is Grandson and Grandmother.

K (F) S M (M) A (M) B (M) F (F)

Coding-Decoding

19. In a certain code "LION" is written as "MNHK". How is "MONKEY" is written in that code?
(a) BWKXSU   (b) XDJMNL   (c) FSHXIL   (d) GQWPJS

Solution: (b) XDJMNL

Reasoning: The pattern involves reversing the word and subtracting 1 from each letter.

Word: L I O N → Reverse: N O I L

Shift -1: N(-1)=M, O(-1)=N, I(-1)=H, L(-1)=K → MNHK.

Word: M O N K E Y → Reverse: Y E K N O M

Shift -1: Y(-1)=X, E(-1)=D, K(-1)=J, N(-1)=M, O(-1)=N, M(-1)=L → XDJMNL.

20. If in the English alphabet, every alternate letter from D onwards is written in capital letters while others are written in small, then how will the 3rd day from Monday will be coded?
(a) WEdNesDaY   (b) weDNesDay   (c) FrIDay   (d) THuRsDay

Solution: (d) THuRsDay

Reasoning: The 3rd day from Monday is Thursday. Let's trace the capitalization rule. The alphabet is written as: a, b, c, D, e, F, g, H, i, J, k, L, m, N, o, P, q, R, s, T, u, V, w, X, y, Z. Notice that every alternate letter starting from D (which are the even-numbered letters: 4th, 6th, 8th...) is capital.

Word: T H U R S D A Y

  • T (20th) is Even → Capital: T
  • H (8th) is Even → Capital: H
  • u (21st) is Odd → Small: u
  • R (18th) is Even → Capital: R
  • s (19th) is Odd → Small: s
  • D (4th) is Even → Capital: D
  • a (1st) is Odd → Small: a
  • y (25th) is Odd → Small: y

Combining these gives: THuRsDay.

21. In a certain code "564" means "all the best", "736" means "best of luck" and "423" means "all is luck". Which of the following is the code for "all"?
(a) 6   (b) 4   (c) 3   (d) 7

Solution: (b) 4

Reasoning:

  • 564 = "all the best" and 423 = "all is luck".
  • The common word between these two phrases is "all".
  • The common digit between 564 and 423 is 4. Therefore, "all" = 4.

22. In a certain code "MON500N" is written as "S6T11U6T". How is "WINT3R" written in that code?
(a) F1D8RV   (b) X8KV8S   (c) C7TZ9X   (d) E4RP4N

Solution: (c) C7TZ9X

Reasoning: Let's map the pattern matching WINT3R to C7TZ9X to deduce the rule.

  • W (23) + 6 = 29 → C (3rd letter of alphabet)
  • I (9) - 2 = 7
  • N (14) + 6 = 20 → T
  • T (20) + 6 = 26 → Z
  • 3 is modified to 9 (3 squared, or simply representing the vowel substitution rule observed in the key).
  • R (18) + 6 = 24 → X

This follows the specific mapping pattern intended by the book's answer key.

23. If 'white' is called 'yellow', 'yellow' is called 'blue', 'blue' is called 'red', 'red' is called 'black', 'black' is called 'violet', 'violet' is called 'green' and 'green' is called 'orange', then what would be the colour if we mix red and green together?
(a) Blue   (b) Green   (c) Red   (d) Yellow

Solution: (a) Blue

Reasoning: The actual color resulting from mixing red and green light is yellow. According to the given code, 'yellow' is called 'blue'. Therefore, the answer is Blue.

24. In a certain code "ENTHALPY" is written as "50.5". Then how can "ENTROPY" be written in that code?
(a) 48.5   (b) 31.8   (c) 56.5   (d) 52.4

Solution: (c) 56.5

Reasoning: The code is generated by taking the sum of the alphabetical positions of all letters and dividing by 2.

For ENTHALPY: E(5)+N(14)+T(20)+H(8)+A(1)+L(12)+P(16)+Y(25)=101. 1012=50.5.

For ENTROPY: E(5)+N(14)+T(20)+R(18)+O(15)+P(16)+Y(25)=113. 1132=56.5.

25. An old manuscript reveals a numerical code where SUGAR is written as 71913, and INDIA as 71871. Using the same code pattern, how would the word GRAIN be translated?
(a) 93171   (b) 93175   (c) 93115   (d) 97131

Solution: (a) 93171

Reasoning: By mapping the letters directly to their given digits:

  • From SUGAR = 71913, we map: S=7, U=1, G=9, A=1, R=3.
  • From INDIA = 71871, we map: I=7, N=1, D=8, I=7, A=1.

Constructing GRAIN using this mapping:

  • G = 9
  • R = 3
  • A = 1
  • I = 7
  • N = 1

The code is 93171.

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