Page 322 - ICSE Math 8

5. Think Smart
1. (a) 4 (b) 1 (c) 3 2. (c)

Chapter 20

Exercise
1. (a) OB, OR, OS (b) PQ (c) SR (d) AB, SR (e) KL
2. diameter = 16 cm; (a) inside the circle (b) on the circle
(c) outside the circle
3. Yes, because length of chord is less than that of diameter.
4. 12 cm 5. 70°
6. (a) 90° (b) Yes (c) 8 cm
6. 7. 8 cm 9. 5 cm ; 12 cm 2
Mental Maths
1. (a) interior (b) diameter (c) one (d) one
(e) point of contact
2. (a) True (b) False (c) True (d) True

Practice Time
1. No, because length of chord is greater than diameter of
the circle.
2. (a) outside the circle (b) on the circle (c) inside the circle
5. 5 cm 6. 6 cm 7. (a) x = y = 45°
(b) x = 55°; y = 27.5° (c) x = 30°; y = 90°
7. (d) x = 12 cm; y = 13 cm
9. 15 cm 10. 30° 11. 9.87 cm 12. 47.14 km
Think Smart
1. 29.96 cm 2.48 inches

Chapter 21

Exercise 21.1
1. 7 cm; 38 cm 2. 1,296 cm 3. 24 m; 36 m 2
2
4. 12 cm; 108 cm 5. ` 1,792 6. 18 cm; 540 cm 2
2
7. 275 m 8. ` 10,626 9. ` 96,000
2
10. 20 m; 8 m; 160 m 11. 1 : 9 12. ` 1,440
2
13. (a) 45 cm (b) 32 cm (c) 763 cm 2
2
2
Exercise 21.2
8.
1. 126 m 2. 36 3cm ; 36 cm
2
2
3. 8 cm; 24 cm 4. ` 1,620 5. 12 m; 21 m 6. 101.808 cm 2
7. (a) 10 cm (b) 24 cm (c) 4.8 cm 8. 6.3 cm
2
9. 216 cm 2
Exercise 21.3
1. 172.5 cm 2. 6 cm 3. 24 cm ; 20 cm 4. 108 cm 2
2
2
5. 12 m; 96 m 6. 25 cm; 35 cm 7. 28 cm
2
8. 240 cm 9. 28 cm 10. 27 cm; 9 cm 11. 306 cm 2
2
12. (a) 175 cm (b) 270 cm 13. ` 1,000
2
2
310