Page 311 - ICSE Math 7

3. (a) Divide both sides by 2 ⇒ x – 1 = 5 Think Smart
Add 1 on both sides ⇒ x = 6 1. Maahi’s age = 16 years; Annie’s age = 34 years
(b) Add 25 on both sides ⇒ 5x = 25 2. 60 marbles
Dividing both sides by 5 ⇒ x = 5 Chapter 14
1 x 1
(c) Subtract from both sides ⇒ = 2 Exercise
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2
Multiply both sides by 2 ⇒ x = 1 1. (a) {–1, 0, 1, 2, …} (b) {1, 2}
(d) Add 2 on both sides ⇒ –x = 8 (c) {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} (d) {10, 11, 12, 13, 14}
Multiply both sides by –1 ⇒ x = –8 (e) {0, 1, 2, 3, 4, 5, 6}
5
4. (a) y = 16 (b) x = 30 (c) x = 63 (d) x = 8 2. (a) {0, 1, 2, 3, 4, 5} (b) {0, 1, 2, 3} (c) {0, 1, 2, 3, 4, 5}
(d) {2, 3, 4, 5} (e) {2, 3, 4, 5} (f) {0, 1, 2, 3, 4}
Exercise 13.3
1. (a) s = –7 (b) m = 2 (c) x = 3 (d) x = 7 3. (a) {7, 8, …}
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(e) x = 11 (f) x = 11 –1 0 1 2 3 4 5 6 7 8
2. (a) 2m = 1, 2m + 3 = 4, 4m – 2 = 0 (b) {2, 3, 4, …}
n
(b) n + 3 = 0, 2n + 6 = 0, + 1 = 0 –1 0 1 2 3 4
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(c) q + 5 = 0, 2q + 10 = 0, 3q + 15 = 0
(d) 5x + 1 = 0, 10x + 2 = 0, 15x = –3 (c) {0, 1} 0 1 2 3
(Note: Answers of Q2 may vary) (d) {0, 1}
0 1 2 3
Exercise 13.4 4. 5 packets
1. 24; 31 2. 36 3. 37 4. 22 years; 66 years Mental Maths
5. 47, 33 6. 29 m; 34 m (a) x + 6 > 12 (b) x + 9 < 4 (c) x – 7 > –14
7. ` 60 per kilogram; ` 120 per kilogram –x x
8. 360 pages 9. 14 m 10. 5 kg (d) x + 4 > 0 (e) –6x > –10 (f) 2 < 6 (g) > –4
2
x
Mental Maths (h) 25 > 4
1. (a) (iii) (b) (iv) (c) (i) Practice Time
2. (a) True (b) False (c) False (d) True (e) True 1. (a) {0, 1, 2, …} (b) {19, 20, 21, …}
3. (a) 12 (b) solution or root (c) 6 (c) {–6, –5, –4, …} (d) {1, 2}
(d) infinite (e) negative
2. (a)
Practice Time 1 2 3 4 5
x x (b)
1. (a) 7x + 4 = 39 (b) x + + = 180° 0 1 2 3 4 5
2
2
2. (a) Divide both sides by 5, Add 2 on both sides (c) –4 –3 –2 –1 0 1 2
5(x – 2) = 10 ⇒ x – 2 = 2 ⇒ x = 2 + 2 ⇒ x = 4
1 3. (a) {…, 0, 1} (b) {…, –4, –3} (c) {5, 6, …}
(b) Subtract from both sides (d) {7, 8, …} (e) {3, 4, …} (f) {…, 0, 1}
4
1 1 3
x + = 1 ⇒ x = 1 – ⇒ x = 4 4. Atmost 3 pairs
4
4
1 –6 Chapter 15
3. (a) x = (b) x = 5
2
4. (a) 4m = –1, 8m + 2 = 0, 2m = –1 Exercise 15.1
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n 1 1. (a) 25° (b) 70° + x (c) 48° 39' 15" (d) 45°
(b) 3n = –2, 9n + 6 = 0, + = 0 2. (a) 95° (b) 135° + x (c) 144° 20' (d) 60°
2
3
(Note: Answer of Q4 may vary)
–1 1 5 3. (a) No (b) Yes (c) Yes (d) Yes (e) Yes
5. (a) 4 (b) 8 (c) (d) 6 (e) 8 4. 40°; 50° 5. 40°; 60°; 80° 6. 80°
3
6. 28; 30; 32 7. Daughter's age = 6 years; My age = 30 years 7. (a) Not adjacent (b) Adjacent (c) Not adjacent
8. length = 40 m, breadth = 20 m 9. 70° 8. (a) 45° (b) 108° (c) 72° 9. 55°; 40°
10. 25 fruit-bearing trees 11. 18 TV sets 12. 22 10. 60° 11. x = 25°; y = 35°
13. ` 287; ` 263 14. 12 12. (a) x = 115° (b) x = 15° (c) x = 30°

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