Page 315 - ICSE Math 8

(b) S = {x: x = n , n ∈ N, n ≤ 7} Mental Maths
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(c) T = {x: x is an odd natural number} 1. (a) (iv) (b) (iii) (c) (i) (d) (ii)
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(d) U = {x: x = 2 n , n ∈ W, n ≤ 5} 2. (a) = (b) ↔ (c) = (d) ↔
(e) V = {x: x = 7n, n ∈ N, n ≤ 6} 3. (a) False (b) True (c) False (d) True (e) True
Exercise 6.2 Practice Time
1. (b), (c) 1. (a) 4 (b) 5 (c) 7 (d) 2
2. (a) Infinite (b) Infinite (c) Finite (d) Finite 2. (a) Infinite (b) Infinite (c) Finite (d) Finite
3. (a), (c), (d) 4. (a) φ, {p}, {q}, {p, q} 3. No 4. (a) Equivalent (b) Equal (c) Equivalent
(b) φ, {–3}, {2}, {4}, {–3, 2}, {–3, 4}, {2, 4}, {–3, 2, 4} 5. (a) 1 (b) 0 (c) 7 (d) 31 6. 3
(c) φ, {–8} (d) φ, {–1}, {0}, {2}, {5}, {–1, 0}, {–1, 2}, 7. 6 8. 9 10. (a) {1, 2, 3, 4, 6, 7, 9, 12, 14, 18, 21, 36, 42}
{–1, 5}, {0, 2}, {0, 5}, {2, 5}, {–1, 0, 2}, {–1, 0, 5}, (b) {1, 2, 3, 6} (c) {4, 9, 12, 18, 36}
{0, 2, 5}, {–1, 2, 5}, {–1, 0, 2, 5} (d) {7, 14, 21, 42} 11. (a) 68 (b) 26
5. A, B and E 6. (a) 5 (b) 7 (c) 4 7. (a) and (c) Think Smart
Exercise 6.3 Rishi and Arnav
1. (a) A ∪ B = {2, 3, 5, 6, 7, 9}; A ∩ B = {3} Chapter 7
(b) C ∪ D = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18}; Exercise 7.1
C ∩ D = {2, 4, 6, 8} 1. (a) 77 (b) 57.31 2. (a) 55.1 (b) 216
(c) E ∪ F = {p, q, r, s, t, v}; E ∩ F = {p, s, t} 3. ` 1,93,874 4. 8,850 L 5. 1,12,500
2. A 4. (a) X ∩ Y = φ 6. (a) ` 1,98,750 (b) ` 1,49,062.50 7. 5.69%
(b) Y ∩ V = {x: x is a prime number > 2} 8. 2,02,800 and 1,15,596 9. 180
(c) Y ∩ Z = {x: x is an odd natural number} 10. 275 11. ` 22,800 12. Milk = 96%; Water = 4%
(d) X ∩ V = {2} (e) Z ∩ V = {x: x is a prime number}
5. (b), (d) Exercise 7.2
6. (a) {5, 15, 25} (b) {4} (c) {8, 12, 14, 16, 24} 1. (a) Increase% = 25% (b) Decrease% = 20%
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(d) {10, 30, 40} (e) {5, 15, 25} (c) Increase% = 50% 2. 600 3. 23 13 % 4. 25%
7. R – Q is the set of irrational numbers 5. 20% 6. 10% 7. 54 8. 50%
9. (a) A′ = {C, O, N, I} (b) B′ = {M, U, A, T}
(c) C′ = {C, O, U} (d) D′ = {O, M, I, T, A} Mental Maths
10. U = { January, February, March, April, May, June, 1. (a) True (b) False (c) True (d) True
July, August, September, October, November, 2. (a) 1,300 (b) 806 (c) 3.85% (d) 81.25
December} Practice Time
A = {April, June, September, November} 1. 38% 2. Decrease% = 6.25% 3. 42.59%
B = { January, March, May, July, August, October, 4. Decrease% = 2% 5. (a) 81.2% (b) 87.31%
December}
C = {January, June, July} 6. ` 14,238 7. (a) 47% (b) 1,000 8. 1,500
D = {April, August} 9. (a) 70% (b) 142.86% 10. ` 2,875 11. 3,36,000 votes
(a) A ∩ C′ = {April, September, November} Think Smart
(b) B′ = {February, April, June, September, November} 1. 16% decrease 2. 108 plants
(c) A ∩ (C ∪ D) = {April, June} Chapter 8
(d) B ∩ D′ = { January, March, May, July, October, Exercise 8.1
December} 1. (a) 7 : 3 (b) Not possible (c) 8 : 11
(e) B ∩ (C ∪ D) = {January, July, August} 2. (a) 8 : 13 > 6 : 11 (b) 16 : 25 > 34 : 59
(f) C′ ∪ D′ = { January, February, March, April, May, (c) 31 : 46 > 14 : 23
June, July, August, September, October,
November, December} 3. (a) ` 682 and ` 372 (b) 1,794 km and 1,014 km
or C′ ∪ D′ = U (c) ` 480, ` 600 and ` 1,320

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