Page 235 - Maths Skills - 7

Answers 233

6. Interior angle Third angle 7. ∠A = 90°, ∠B = 60°, ∠C = 30°
(i) 75° 60° 8. a = b + c (Given)
(ii) 60° 85° a + b + c = 180° (Angle sum property)
(iii) 38° 122° ⇒ a + a = 180° ( b + c = a)
(iv) 70° 50° ⇒ 2a = 180°, ⇒ a = 90°
9. 42° 10. 40°, 80 and 60° 11. 70° 12. 30°, 30° 13. 720°
14. ∠A = 65°, ∠B = 60°, ∠AED = 55° 15. ∠x = 25°, ∠y = 25° 16. ∠A = 50°, Yes 17. (i) 70° (ii) 60° (iii) 100°
18. (i) ∠ACB = 120°, (ii) ∠ACD = 60°, (iii) ∠AEB = 150°
Exercise - 10.2

1. (i) < (ii) > (iii) < 2. Do it yourself 3. (vi) 4. No 5. (i) Yes (ii) No (iii) No

Exercise - 10.3
1. (i) ∠ABC = 75° and ∠ACB = 75° (ii) ∠DBC = 50° and ∠DCB = 50° (iii) x = 25°
2. ∠Q = ∠R
3. (i) PQ = PR (ii) VW = VU (iii) ZY = ZX 4. (i) ∠PQR = 60° and ∠PRQ = 60° (ii) ∠SQR = 70° and ∠SRQ = 70°
(iii) ∠PQS = 130°, ∠PRS = 130°; yes 5. X = 30°, Y = 60°, Z = 60° 6. YX = YZ
7. (i) ∠Q = ∠R (ii) ∠U = ∠V (iii) ∠X = ∠Z 8. (i) ∠PQR = 80° and ∠PRQ = 20° (ii) ∠a = 100°, ∠b = 160°

Exercise - 10.4
1. Do it yourself 2. 20 m 3. 10 km 4. 50 m 5. 34 cm 6. (i) 26 cm (ii) 25 cm 7. 49 m 8. 8 cm each

Assessment Time

A. 1. (iv) 2. (iii) 3. (ii) 4. (ii) 5. (iii)
2
B. 1. 90° 2. 70° 3. obtuse angled triangle 4. isosceles 5. QR + PQ 2
C. 1. F 2. T 3. T 4. F 5. F D. 1. (iv) 2. (i) 3. (ii)
4. (iii) 5. (iv) E. 1. (a) 2. (b) 3. (b) F. 1. 7 cm each 2. 21 m
G. 1. Because 9, 12, 15 make a right angled triangle 9 + 12 = 15 2
2
2
2. A A
15 D D
9 E

B 12 F C B C
here BD, EC, AF are three Median here AD, BC are also the altitude BD is another altitude

3. Yes, 30 = 5 + 12 + 13 ⇒ 5 + 12 = 13 4. Yes, 3, 4, 5; 6, 8, 10 5. right angled triangle (5, 12, 13)
2
2
2
HOTS
1. 90°, 60°, and 30° 2. x = 95° and y = 130°
3. PQ = 10 cm 4. (i) ∠ABD = 30°, ∠ACB = 30° and ∠CBD = 60° (ii) The new triangle will have same shape but different size.

Chapter - 11: Symmetry
Boot-up

A. 1. (ii) 2. (iii) 3. (iii) 4. (iv) B. 1. infinite 2. bisector 3. three 4. axis
C. 1. F 2. T 3. T 4. F

Exercise - 11.1
1. (i), (ii), (iii), (iv) 7. (i) 1 (ii) 0 (iii) 4 (iv) 5 (v) 6 (vi) 7 (vii) 8 (viii) 2
Exercise - 11.2
2. (i) Reflection and Rotational symmetry (ii) Reflection and Rotational symmetry (iii) Rotational symmetry
(iv) Reflection symmetry 3. (i) infinite (ii) four (iii) 0, 1 (iv) infinite, order two
(v) two (vi) mirror/linear symmetry 4. (i) 3 (ii) 5 (iii) 6