Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 +...

14
Active Maths 2 (Strands 1–5): Ch 1 Solutions Chapter 1 Exercise 1.1 Q. 1. (i) Not well defined, as the meaning of the term ‘inexpensive’ is subjective. (ii) Well defined. (iii) Not well defined, as the meaning of the term ‘large‘ is subjective. (iv) Well defined. Q. 2. (i) A B = {0, 2, 3, 4, 5, 6, 7, 8} (ii) A B = {2} (iii) A’ = {0, 1, 4, 6, 8} (iv) B’ = {1, 3, 5, 7} (v) A \ B = {3, 5, 7} (vi) B \ A = {0, 4, 6, 8} (vii) (A B)’ = {1} (viii) A’ B = {0, 1, 2, 4, 6, 8} Q. 3. (a) U A B • 21 • 25 • 20 • 22 • 24 • 23 (b) (i) A B = {21, 23, 25} (ii) A B = {23} (iii) A’ = {20, 22, 24} (iv) B’ = {20, 21, 22, 24, 25} (v) (A B)’ = {20, 21, 22, 24, 25} (vi) A’ B’ = {20, 21, 22, 24, 25} (vii) B \ A = {} or (viii) (A \ B) (B \ A) = {21, 25} (c) A \ B’ = {23} B \ A’ = {23} A \ B’ = B \ A’ Answer is yes (d) As B = A B B A (e) Case 1 # (A B) = 0 # (A B) = 0 In this case # (A B) = # (A B) Case 2 # (A B) > 0 and # (A B) = 0 In this case # (A B) > # (A B) Case 3 # (A B) > 0 and # (A B) > 0 As A B is a subset of A B, # (A B) > # (A B) Q. 4. (i) 2 3 = 8 (ii) {}, {x}, {y}, {z}, {x, y}, {x, z}, {y, z}, {x, y, z} (iii) {x, y, z} Q. 5. (i) A B (iii) (A B)’ (ii) A B (iv) B \ A Q. 6. (i) U X Y (ii) U X Y (iii) X Y U (iv) U X Y 1

Transcript of Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 +...

Page 1: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

Active Maths 2 (Strands 1–5): Ch 1 Solutions

Chapter 1 Exercise 1.1

Q. 1. (i) Not well defined, as the meaning of the term ‘inexpensive’ is subjective.

(ii) Well defined.

(iii) Not well defined, as the meaning of the term ‘large‘ is subjective.

(iv) Well defined.

Q. 2. (i) A ∪ B = {0, 2, 3, 4, 5, 6, 7, 8}

(ii) A ∩ B = {2}

(iii) A’ = {0, 1, 4, 6, 8}

(iv) B’ = {1, 3, 5, 7}

(v) A \ B = {3, 5, 7}

(vi) B \ A = {0, 4, 6, 8}

(vii) (A ∪ B)’ = {1}

(viii) A’ ∪ B = {0, 1, 2, 4, 6, 8}

Q. 3. (a) U

A B

• 21

• 25

• 20 • 22 • 24

• 23

(b) (i) A ∪ B = {21, 23, 25}

(ii) A ∩ B = {23}

(iii) A’ = {20, 22, 24}

(iv) B’ = {20, 21, 22, 24, 25}

(v) (A ∩ B)’ = {20, 21, 22, 24, 25}

(vi) A’ ∪ B’ = {20, 21, 22, 24, 25}

(vii) B \ A = {} or ∅

(viii) (A \ B) ∪ (B \ A) = {21, 25}

(c) A \ B’ = {23}

B \ A’ = {23}

∴ A \ B’ = B \ A’

Answer is yes

(d) As B = A ∩ B

⇒ B ⊂ A

(e) Case 1 # (A ∪ B) = 0 ⇒ # (A ∩ B) = 0 In this case # (A ∪ B) = # (A ∩ B)

Case 2 # (A ∪ B) > 0 and # (A ∩ B) = 0 In this case # (A ∪ B) > # (A ∩ B)

Case 3 # (A ∪ B) > 0 and # (A ∩ B) > 0 As A ∩ B is a subset of A ∪ B,

# (A ∪ B) > # (A ∩ B)

Q. 4. (i) 23 = 8

(ii) {}, {x}, {y}, {z}, {x, y}, {x, z}, {y, z}, {x, y, z}

(iii) {x, y, z}

Q. 5. (i) A ∪ B (iii) (A ∩ B)’

(ii) A ∩ B (iv) B \ A

Q. 6. (i) U

X Y

(ii) U

X Y

(iii)

X Y

U

(iv) U

X Y

1

Page 2: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

2 Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 7. (a) U = {1, 2, 3, 4, 5, 6, 7, 8}

O = {1, 3, 5, 7}

P = {3, 5, 7}

(b)

• 4 • 6 • 8• 2

U

O P

• 3

• 5

• 7

• 1

(c) (i) 4

(ii) 3

(iii) 3

(iv) 1

(v) 4

(vi) 4

(d) = ; =

Q. 8. (i)

271

U(500)

I(103) S(146)

2083 126

83 + 20 + 126 = 229

500 − 229 = 271

(ii) 83 + 126 = 209

209 ____ 500 × 100 ____ 1 % = 41.8%

Q. 9. (i)

170

U(400)

G(150) V(100)

20130 80

150 + 100 + 170 = 420

420 − 400 = 20

(ii) 20

(iii) 80 ____ 400 × 100 ____ 1 % = 20%

(iv) 130 + 80 = 210

210 ____ 400 × 100 ____ 1 % = 52.5%

Q. 10. (i) {0} is the set containing the element 0 whereas ∅ is the set containing zero elements.

(ii) 0 is the element ‘zero’ whereas {0} is the set containing the element 0.

(iii) X and Y are disjoint (mutually exclusive) sets.

(iv) X and Y are both empty; X = Y = {}.

(v) X ∩ Y = X

(vi) X ∪ Y = Y

(vii) X = Y

Q. 11. (i) U

A B

Ans: A

(ii) U

A B

Ans: A ∩ B

(iii) U

A B

Ans: A ∪ B

(iv) U

A B

Ans: ∅

Page 3: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

3Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 12. (i) U

A B

(ii) U

A B

(iii) D

= (A \ B) ∪ (B \ A)

= (A ∪ B) \ (A ∩ B)

Q. 13. (i) A3 = {4k: k ∈ N} = {4, 8, 12, 16, 20, ……}

∴ First five elements are 4, 8, 12, 16, 20.

(ii) A1 = {2k: k ∈ N} = {2, 4, 6, 8, 10, 12, ……}

A2 = {3k: k ∈ N} = {3, 6, 9, 12, 15, 18, …….}

∴ A1 ∩ A2 = {6, 12, 18, 24, ….} = A5

Q. 14. (i) U(430)

H(250)

x

G(240)

3x250 – 3x 240 – 3x

(ii) Total Number = 250 + 240 − 3x + x

Total Number = 490 − 2x

(iii) 490 − 2x = 430

60 = 2x

x = 30

Exercise 1.2

Q. 1. (i)

B

U

C

A

(ii) B

U

C

A

(iii)

B

U

C

A

(iv)

B

U

C

A

(v)

B

U

C

A

Page 4: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

4 Active Maths 2 (Strands 1–5): Ch 1 Solutions

(vi) B

U

C

A

Q. 2. (i) A ∩ B ∩ C

(ii) A \ (B ∪ C)

(iii) (B ∩ C) \ A

(iv) (A ∪ B ∪ C)’

Q. 3. (i) {4, 5}

(ii) {2, 8}

(iii) {8}

(iv) {2}

(v) {2, 3, 4, 5, 6, 8, 9}

(vi) {7}

Q. 4. (i) {0, 1, 2, 3, 5, 6, 8, 9}

(ii) {0}

(iii) {9}

(iv) {6}

(v) {0, 6, 9}

(vi) {4, 7}

Q. 5. (i) (X ∩ Y) \ Z

(ii) X \ Y

(iii) Z \ (X ∪ Y)

(iv) (X ∪ Y ∪ Z)’

Q. 6.

Y

U

Z

• 7

X

• 6

• 5• 1• 3

• 4• 2 • 0

Q. 7. (a) Q

U

R

• 8

P

• 7

• 5• 6

• 2• 1

• 3

• 4

(b) (i) {1}

(ii) {5, 6}

(iii) {1, 2, 3, 4, 5, 6, 7}

(iv) {6}

(v) {3, 4, 5, 7, 8}

(vi) {8}

(vii) {1}

(viii) ∅

(ix) {1, 7, 8}

(x) {1, 5, 6, 7}

(xi) {1, 6}

(xii) {1}

Q. 8. (i)

Y

U

Z

X

• f

• c• d

• b• a • e

(ii) {b, c}

(iii) {d}

(iv) 6

(v) (Y ∩ Z) \ X

Q. 9. (i)

B

U

C

A

• 1 • 9

• 3• 5• 7

• 2

• 4

• 6

• 8

Page 5: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

5Active Maths 2 (Strands 1–5): Ch 1 Solutions

A = {2, 3, 5, 7}

B = {2, 4, 6, 8}

C = {1, 3, 5, 7, 9}

U = {1, 2, 3, 4, 5, 6, 7, 8, 9}

(ii) {3, 5, 7}

(iii) {2}

(iv) # (A ∪ B ∪ C) = 9 = # U

(v) A \ (B ∪ C)

A ∩ B ∩ C

(B ∩ C) \ A

U \ (A ∪ B ∪ C)

Q. 10. (i) A = {2, 3}

B = {1, 2, 3, 4, 6, 12}

C = {1, 2, 4, 8}

(ii)

B

U

C

A

• 8

• 9

• 10

• 11

• 5

• 7

• 3

• 2 • 4• 1

• 6

• 12

(iii) {1, 2, 4}

(iv) {2}

(v) 7

(vi) A \ (B ∪ C)

(A ∩ C) \ B

Q. 11. (i) P ∩ Q ∩ R

(ii) P ∪ Q ∪ R

(iii) Q

(iv) Q \ (P ∪ R)

(v) P ∩ R

(vi) (P ∩ Q) \ R

(vii) R’

(viii) (P ∪ Q ∪ R)’

Q. 12. (i)

N

U

Z

P

• 0

• –2

• –10

• 1

2

• √3

• 9.0321

• 3

• 5• 2

• 23

• 1 • 4

(ii) N \ Z and P \ N

(iii) (a) P ⊂ N

(b) N ⊂ Z

Q. 13. A = {1, 2, 3, 4, 5, …., 18, 19, 20}

B = {2, 5, 8, 11, …….} (i.e. = {2, 5, 8, 11, 14, 17, 20, ….})

C = {3, 5, 7, 9, …….} (i.e. = {3, 5, 7, 9, 11, 13, 15, 17, 19,

….})

(a) {5, 11, 17}

(b) {2, 8, 14, 20}

(c) {3, 7, 9, 13, 15, 19}

Exercise 1.3

Q. 1. (i) 2

(ii) 6

(iii) 15

(iv) 5

(v) 19

(vi) 23

(vii) 21

Q. 2. (i) U(70)

B(30)

S(37)

M(35)

153

5710

1012 8

(ii) 3

Page 6: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

6 Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 3. (i) U(100)

S(48)

B(43)

R(55)

166

10

98

1422 15

(ii) 6

Q. 4. (i) U(30)

I(19)

G(12)

F(15)

21

5

23

105 2

(ii) 5

(iii) 2

(iv) 1 ___ 30

Q. 5. (i) L1(23)

L2(21)

L(31)

7

5

45

1015 6

(ii) 15

Q. 6. (i) 10 + 4 + 3 + 8 + 15 + 5 + 1 = 46

∴ x = 50 − 46

∴ x = 4

(ii) 7

Q. 7. (i) 7 + 10 + 6 + 9 + 2 = 34

45 − 34 = 11

∴ 3x + x + 5 − x = 11

⇒ 3x = 6

⇒ x = 2

(ii) # R = 9 + 6 + 5 = 20

Q. 8. (i)

T(16)

U(40)

C(18)

P(19)

86

2

26

11 – x 12 – xx

(ii) 18 + 12 + 11 − x + 6 = 40

47 − x = 40

x = 7

(iii) 4

(iv) 2 ___ 40 = 1 ___ 20 = 5%

(v) 26 ___ 40 = 13 ___ 20 = 65%

(vi) 17 ___ 40 = 42.5%

Q. 9. (i) S

U(100)

C(50)

A(41)

252

x16

5 2520 – x

9 – x

(ii) 41 + 2 + 25 + 9 − x = 77 − x

100 − (77 − x) = 25

23 + x = 25

x = 2

(iii) 46

(iv) 52

(v) 43

(vi) 93%

(vii) 57%

Q. 10. (i) B(18)

U = 39

C

P(23)

34

x

6 9 – x

11 – x 7

Page 7: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

7Active Maths 2 (Strands 1–5): Ch 1 Solutions

(ii) 6 + (9 − x) + x + (11 − x) = 23

26 − x = 23

−x = 23 − 26

−x = −3

x = 3

(iii) 18 − [9 − x + x + 7] = 18 − 16

= 2

Two liked Brussels sprouts only.

(iv) 9 − 3 = 6

Six students liked Brussels sprouts and peas but not cauliflower.

Q. 11. (i) Tulips

U = 40

Daffodils

5

4

20

x 3

Roses

(28)

20 + 4 + 3 + x = 30

27 + x = 30

∴ x = 3

Tulips

U = 40

Daffodils

35

4

20 y1

3 3

Roses

(28)

28 + 3 + 3 + y + 5 = 40

39 + y = 40

∴ y = 1

(ii) P(roses or daffodils) = 34 ___ 40

= 17 ___ 20

(iii) P(roses and daffodils but not

tulips) = 3 ___ 40

Q. 12. (i)

B(13)

U = 35

SF(16)

55

7

1 49

3 1

NY(20)

(ii) P(None of the three cites) = 5 ___ 35

= 1 __ 7 (iii) P(New York only) = 9 ___ 35

(iv) P(Boston or New York) = 25 ___ 35

= 5 __ 7

Exercise 1.4

Q. 1. (i) B

U

C

• 1 • 6

• 8

• 7

• 4

• 5

• 0• 3

• 2 • 9

A

Page 8: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

8 Active Maths 2 (Strands 1–5): Ch 1 Solutions

(ii) (A ∪ B) ∪ C = {0, 2, 3, 4, 5, 7, 8, 9} ∪ {1, 2, 6, 7, 8, 9} = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

A ∪ (B ∪ C) = {2, 3, 7, 8} ∪ {0, 1, 2, 4, 5, 6, 7, 8, 9} = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} ∴ (A ∪ B) ∪ C = A ∪ (B ∪ C)

(iii) (A ∩ B) ∩ C = {7, 8} ∩ {1, 2, 6, 7, 8, 9} = {7, 8}

A ∩ (B ∩ C) = {2, 3, 7, 8} ∩ {7, 8, 9} = {7, 8} ∴ (A ∩ B) ∩ C = A ∩ (B ∩ C)

(iv) (A \ B) \ C = {2, 3} \ {1, 2, 6, 7, 8, 9} = {3}

A \ (B \ C) = {2, 3, 7, 8} \ {0, 4, 5} = {2, 3, 7, 8} ∴ (A \ B) \ C ≠ A \ (B \ C)

Q. 2. (i)

B

U

C

• 10

• 2

• 9• 7

• 1• 0

• 5

• 4 • 8

• 3

• 6

A

(ii) A ∪ (B ∩ C) = {0, 2, 4, 5, 9} ∪ {2, 8} = {0, 2, 4, 5, 8, 9}

(A ∪ B) ∩ (A ∪ C) = {0, 1, 2, 4, 5, 7, 8, 9} ∩ {0, 2, 4, 5, 8, 9, 10} = {0, 2, 4, 5, 8, 9}

∴ A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C)

(iii) A ∩ (B ∪ C) = {0, 2, 4, 5, 9} ∩ {1, 2, 4, 7, 8, 9, 10} = {2, 4, 9}

(A ∩ B) ∪ (A ∩ C) = {2, 9} ∪ {2, 4} = {2, 4, 9}

∴ A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C)

Q. 3. (i) (P ∪ Q) ∪ R = {b, c, d, e, f, g, h} ∪ {a, b, c, h}

= {a, b, c, d, e, f, g, h}

P ∪ (Q ∪ R) = {b, c, d, e, f} ∪ {a, b, c, e, f, g, h}

= {a, b, c, d, e, f, g, h}

∴ (P ∪ Q) ∪ R = P ∪ (Q ∪ R)

(ii) (P ∩ Q) ∩ R = {e, f} ∩ {a, b, c, h} = ∅

P ∩ (Q ∩ R) = {b, c, d, e, f} ∩ {h} = ∅

∴ (P ∩ Q) ∩ R = P ∩ (Q ∩ R)

Page 9: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

9Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 4. (i) X ∪ (Y ∩ Z) = {s, t, v, w} ∪ {u, z} = {s, t, u, v, w, z}

(X ∪ Y) ∩ (X ∪ Z) = {s, t, v, w, u, y, z} ∩ {s, t, v, w, u, x, z}

= {s, t, v, w, u, z}

∴ X ∪ (Y ∩ Z) = (X ∪ Y) ∩ (X ∪ Z)

(ii) X ∩ (Y ∪ Z) = {s, t, v, w} ∩ {u, w, y, z, s, x} = {s, w}

(X ∩ Y) ∪ (X ∩ Z) = {w} ∪ {s} = {s, w}

∴ X ∩ (Y ∪ Z) = (X ∩ Y) ∪ (X ∩ Z)

Q. 5. (X ∪ Z) ∪ Y = X ∪ (Z ∪ Y)

= X ∪ (Y ∪ Z)

= (X ∪ Y) ∪ Z

Q. 6. M ∪ (N ∩ O)

Q. 7. (T ∩ R) ∪ (T ∩ S)

Q. 8. (i) A’

(ii) B’

(iii) (A ∪ B)’ = Region 1

(iv) (A ∪ B)’ = A’ ∩ B’

(v) (A ∩ B)’

(vi) (A ∩ B)’ = A’ ∪ B’

Q. 9. B

U

C

• 6

• 7• 5

• 9• 3

• 2•8

•4•10• 1

A

(i) (A ∪ B)’ = {1, 6}

A’ ∩ B’ = {1, 4, 6, 8, 9, 10} ∩ {1, 2, 3, 6} = {1, 6}

∴ (A ∪ B)’ = A’ ∩ B’

(ii) (A ∩ C)’ = {1, 3, 4, 5, 6, 7, 8, 9, 10}

A’ ∪ C’ = {1, 4, 6, 8, 9, 10} ∪ {1, 3, 5, 7, 9} = {1, 3, 4, 5, 6, 7, 8, 9, 10}

∴ (A ∩ C)’ = A’ ∪ C’

(iii) A’ = {1, 4, 6, 8, 9, 10}

∴ (A’)’ = {2, 3, 5, 7} = A

(iv) A ∪ (B ∩ C) = {2, 3, 4, 5, 7, 8, 10}

(A ∪ B) ∩ (A ∪ C) = {2, 3, 4, 5, 7, 8, 9, 10} ∩ {2, 3, 4, 5, 6, 7, 8, 10}

= {2, 3, 4, 5, 7, 8, 10}

∴ A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C)

(v) A ∩ (B ∪ C) = {2, 5, 7}

(A ∩ B) ∪ (A ∩ C) = {5, 7} ∪ {2} = {2, 5, 7}

∴ A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C)

Page 10: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

10 Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 10. (i) (A’ ∪ B)’ = (A’)’ ∩ B’ = A ∩ B’ = {2, 3, 7, 8} ∩ {1, 2, 3, 6}

= {2, 3}

(ii) U

A B

• 7

• 8• 3

• 2

• 1 • 6

• 4

• 5

• 10

• 9

(A ∩ B’)’ = A’ ∪ (B’)’ = A’ ∪ B = {1, 4, 5, 6, 9, 10} ∪ {4, 5, 7, 8, 9, 10}

= {1, 4, 5, 6, 7, 8, 9, 10}

(A’ ∪ B)’ = {1, 4, 5, 6, 7, 8, 9, 10}’

= {2, 3}

(A ∩ B’)’ = {2, 3}’

= {1, 4, 5, 6, 7, 8, 9, 10}

∴ Answers verified

Revision Exercises

Q. 1. U = {1, 2, 3, 4, …, 19, 20}

A = {1, 2, 4, 5, 10, 20}

B = {2, 4, 6, 8, …, 18, 20}

(a) U

A B

• 2

• 10

• 20

• 4

• 5

• 1

• 3 • 7 • 9 • 11 • 13

• 15

• 17

• 19• 6

• 16

• 18

• 8• 12

• 14

(b) (i) {1, 2, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20}

(ii) {2, 4, 10, 20}

(iii) {3, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19}

(iv) {1, 3, 5, 7, 9, 11, 13, 15, 17, 19}

(v) {1, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19}

(vi) {1, 3, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15, 16, 17, 18, 19}

(vii) {1, 5, 6, 8, 12, 14, 16, 18}

(viii) ∅

Page 11: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

11Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 2. (i) 4 (iv) 2

(ii) 4 (v) 6

(iii) 2 (vi) 2

Q. 3. (i) Y

Z

• v

• w• y• z

• s• t

• u• x

X

(ii) {w, y, z}

(iii) ∅

(iv) 8

(v) {X \ (Y ∪ Z)

(vi) {Y \ (X ∪ Z)

(X ∩ Y) \ Z

(X ∩ Z) \ Y

(Y ∩ Z) \ X

Q. 4. (i) T(1248)

U

J(1424)

480

1026

222

190 532

260116234

B(762)

(ii) 762 + 260 + 532 + 480 + 1026 = 3,060

(iii) 2034 _____ 3060 × 100 ____ 1 % = 66.47%

(iv) 856 _____ 3060 × 100 ____ 1 % = 27.97%

(v) 1554 _____ 3060 × 100 ____ 1 % = 51%

Q. 5. A = {2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30}

B = {3, 6, 9, 12, 15, 18, 21, 24, 27, 30}

C = {5, 10, 15, 20, 25, 30}

(i) B

U

C

• 7

• 17

• 19 • 23

• 29• 11

• 13

116

• 5 • 25

• 30

• 6• 2

• 4

• 8

• 14

• 16

• 22

• 26

• 28

• 12• 18• 24

• 10

• 20 • 15

A• 3

• 9

• 21

• 27

(ii) (A ∪ B) ∪ C = {2, 4, 8, 14, 16, 22, 26, 28, 10, 20, 6, 12, 18, 24, 30, 3, 9, 21, 27, 15}

∪ {10, 20, 30, 15, 25, 5}

= {2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30}

A ∪ (B ∪ C) = {2, 4, 8, 14, 16, 22, 26, 28, 10, 20, 6, 12, 18, 24, 30}

∪ {6, 12, 18, 24, 30, 3, 9, 21, 27, 15, 10, 20, 5, 25}

= {2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30}

∴ (A ∪ B) ∪ C = A ∪ (B ∪ C)

Page 12: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

12 Active Maths 2 (Strands 1–5): Ch 1 Solutions

(iii) (A ∩ B) ∩ C = {6, 12, 18, 24, 30} ∩ {5, 10, 15, 20, 25, 30} = {30}

A ∩ (B ∩ C) = {2, 4, 6, 8, 10, 12, …, 28, 30} ∩ {15, 30} = {30}

∴ (A ∩ B) ∩ C = A ∩ (B ∩ C)

(iv) (A \ B) \ C = {2, 4, 8, 10, 14, 16, 20, 22, 26, 28} \ {5, 10, 15, 20, 25, 30}

= {2, 4, 8, 14, 16, 22, 26, 28}

A \ (B \ C) = {2, 4, 6, 8, …., 28, 30} \ {3, 6, 9, 12, 18, 21, 24, 27}

= {2, 4, 8, 10, 14, 16, 20, 22, 26, 28, 30}

∴ (A \ B) \ C ≠ A \ (B \ C)

(v) A ∪ (B ∩ C) = {2, 4, 6, …., 28, 30} ∪ {15, 30}

= {2, 4, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 24, 26, 28, 30}

(A ∪ B) ∩ (A ∪ C) = {2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 3, 9, 15, 21, 27}

∩ {5, 10, 15, 20, 25, 30, 2, 4, 6, 8, 12, 14, 16, 18, 22, 24, 26, 28}

= {2, 4, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 24, 26, 28, 30}

∴ A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C)

(vi) A ∩ (B ∪ C) = {2, 4, 6, 8, …., 28, 30} ∩ {5, 10, 15, 20, 25, 30, 3, 6, 9, 12, 18, 21, 24, 27}

= {6, 10, 12, 18, 20, 24, 30}

(A ∩ B) ∪ (A ∩ C) = {6, 12, 18, 24, 30} ∪ {10, 20, 30} = {6, 10, 12, 18, 20, 24, 30}

∴ A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C)

Q. 6. (i) P(25)

U(49)

O(26)

6

5

8

3 9

17 – x 8 – xx

A(28)

(ii) 28 + 8 − x + 9 + 6 + 5 = 49

56 − x = 49

x = 7

(iii) 10 + 1 + 6 ___________ 49 = 17 ___ 49 × 100 ____ 1 %

≈ 35%

Q. 7. (i) U(30)

P(16) Q(6)

x16 – x 6 – x

y

To minimise y

maximise 16 + 6 − x = 22 − x

Let x = 0

⇒ Ans = 8

(ii) To maximise y, minimise 16 + 6 − x = 22 − x

Let x = 6

⇒ Ans = 14

(iii) U(u)

P(p) Q(q)

qp – q o

x

∴ u = p − q + q + o + x

∴ u = p + x

Page 13: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

13Active Maths 2 (Strands 1–5): Ch 1 Solutions

Q. 8. (i)

B(25)

U

C(31)

0

116

7

8

15 – (x + y)1 + x – y

16 – x

y

x

F(23)

B(25)

U

C(31)0

116

7

8

210

5

2

11

F(23)

43 = 25 + 7 + x 23 + 17 − y = 3843 = 32 + x 40 − y = 38 x = 11 y = 2

(ii) 45 (iii) 26 ___ 45 × 100 ____ 1 % ≈ 58% (iv) 19 ___ 45 × 100 ____ 1 % ≈ 42%

Q. 9. (a) (i) {1, 2, 3, 4, 5, 6}

(ii) {5, 6}

(iii) {1, 2, 4, 5, 6}

(b) (P ∪ Q) ∩ (P ∪ R)

Q. 10. (a) 7 (b) One (c) Prime

Q. 11. (a) C

U(100)

D

24

116

8

4

2622

5

3

8

T(41)

(b) 41 + 22 + 5 ____________ 100 = 68 ____ 100 = 17 ___ 25 = 68%

(c) 3 ____ 100 = 3%

Q. 12. (i) B

C

A

• 6

• 1• 4

• 2

• 3• 5

(A \ B) ∪ (C ∩ B) = {1, 4, 3, 5}

= {1, 3, 4, 5}

(A ∪ B) ∩ (C \ B) = {1, 4}

(ii) U(20)

P

4

Q

x2x 5x

8x + 4 = 20

8x = 16

x = 2

# Q = 12

Q. 13. (a) U(110)

W(82)

15

S(57)

4438 13

82 + 57 = 139

139 + 15 = 154

154 − 110 = 44

82 − 44 = 38

57 − 44 = 13

Page 14: Chapter 1 Exercise 1 - Biology Leaving Cert. Sets 2.pdf · Daffodils 5 4 20 x 3 Roses (28) 20 + 4 + 3 + x = 30 27 + x = 30 ∴ x = 3 Tulips U = 40 Daffodils 3 5 4 1 20 y 3 3 Roses

14 Active Maths 2 (Strands 1–5): Ch 1 Solutions

(b) (i) U(u)

A(a)

y

B(b)

xa – x b – x

u = a + b − x + y

(ii) To minimise u, maximise x.

For maximum x, set b − x = 0 (as a > b)

⇒ b = x

⇒ u = a + (x) − x + y

⇒ u = a + y

⇒ u = y + a