Page 343 - Start Up Mathematics_7

Thinking Skills Answer in One Word or a Line

1. 400 2. 2,16,000 3. ` 5,176.47 1. Two angles are said to be supplementary if their sum is
180°.
4. ` 4,000 5. 22%
2. Linear pair 3. 2 pair, 4 pairs
Values and Life Skills 4. Two obtuse angles cannot form a linear pair as their sum
3 is greater than 180°.
1. 66 % 2. 30% 3. ` 22,000
5 5. Not necessarily, the non-common arms should be on either
Exemplar Problems side of the common arm
1. d 2. c 3. d 4. b Let’s Evaluate
5. True 6. ` 8,000 7. 48 ≠ 36 1. x = 40° 2. ∠1 = 100°, ∠2 = ∠3 = 80°

3. x = 120°, y = 115°
Chapter 9
4. ∠2 = ∠5 = ∠6 = 80°; ∠3 = ∠4 = 100°
Exercise 9.1 5. (a) not parallel (b) not parallel (c) parallel
1. (a) 30° (b) 8° (c) 65° 2. (a) 12° (b) 118° (c) 175° (d) not parallel (Reasons may vary) 6. x = 35°
3. Complementary: (a), (b), (d), (e), (h) Thinking Skills
Supplementary: (c), (f), (g) 4. 120° 1. All pairs of alternate interior angles will also be equal.
5. (a) 114° (b) 60° 6. ∠2 = 140°, ∠1 = ∠3 = 40° 2. (a) x = 255° (b) y = 108°
7. x = 34°, ∠1 = 58°, ∠2 = 122° 8. 172° 3. (a) x = 80°, y = 140° (b) x = y = 60°
Exercise 9.2 4. (a)  l m  corresponding angles are not equal.

1. ∠1 = ∠5 = ∠7 = 55°; ∠2 = ∠4 = ∠6 = ∠8 = 125° (b) ∠4, ∠9, ∠12
2. 108°, 72° (c) ∠2, ∠3, ∠10, ∠11
3. ∠1 = ∠3 = ∠5 = ∠7 = 60°; ∠2 = ∠4 = ∠6 = ∠8 = 120° (d) ∠3 = ∠10, ∠4 = ∠9; ∠3 ≠ ∠6, ∠4 ≠ ∠5
4. ∠1 = ∠3 = 68°; ∠2 = ∠4 = 112° Exemplar Problems
5. x = 50°, y = 85°, z = 45° 1. b 2. b 3. b 4. arm
6. x = 75°, y = 75°, z = 105° 5. True 6. 20, 40°, 30°

7. (a) y = 110°, x = 70° (b) x = 60°, 2x = 120° 7. Students to do on their own.
(c) x = 120°, y = 60° A Challenge!
8.  AB || CD (alternate interior angles are equal) and The 3 obvious cases are: a || b ; g || h ; i || j
EF || CD (sum of co-interior angles is supplementary) The remaining 7 cases are: a || f ; b || f ; a || n ; b || n
hence AB || EF. f || n ; g || e ; h || e
9. 130° Chapter 10
Review Exercises
Multiple Choice Questions Exercise 10.1
1. (a) Isosceles (b) Scalene (c) Equilateral
1. c 2. c 3. d 4. a 5. b
2. (a) Acute (b) Obtuse (c) Right
6. a 7. c 8. a 9. d 10. a
3. ∠ACD = 120° 4. 85°, 50° 5. 30°
Solve Mentally
True or False 7. 40° and 80° 8. 30°, 60°, 90°
1. True 2. False 3. True 4. True 5. True 9. (a) x = 45° , y = 135° (b) x = 135° , y = 225°
6. True (c) x = 60° , y = 40° (d) x = 65° , y = 40°
Fill in the Blanks (e) x = 50° , y = 70°

1. intersecting 2. 180° 3. corresponding Exercise 10.2
4. linear pair 5. vertically opposite 1. (a) Yes (b) No (c) Yes (d) Yes
6. 180° 7. adjacent 8. 65°, 115° 2. (b) and (c) are always true

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