Page 285 - ICSE Math 6

Chapter 4 3. (a) 27 (b) 3 (c) 221 (d) 2 (e) 90 (f) 1
Exercise 4.1 (g) 270 (h) 663 4. 15 5. 133 6. 15 kg
1. (a) 1, 3, 9, 27 (b) 1, 2, 3, 4, 6, 9, 12, 18, 36 Exercise 4.6
(c) 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60 1. (a) 45 (b) 48 (c) 4,680 (d) 264 (e) 2,448
(d) 1, 2, 4, 5, 10, 11, 20, 22, 44, 55, 110, 220 (f) 2,880
(e) 1, 2, 3, 6, 29, 58, 87, 174
2. (a) No (b) No (c) Yes (d) Yes 2. (a) 60 (b) 2,800 (c) 12,432 (d) 19,800 (e) 900
3. Prime numbers: 17, 83, 29 (f) 264
Composite numbers: 56, 122, 99 3. (a) 27 (b) 75 (c) 200 (d) 48 (e) 1,680 (f) 216
4. 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47 4. 144 5. 1,084 6. (a) 35 (b) 19
5. (a) 2, 4, 6, 8, 10, 12 (b) 5, 10, 15, 20, 25 7. LCM = 270; HCF = 9 8. 169
(c) 10, 20, 30, 40, 50, 60, 70, 80, 90, 100 Mental Maths
(d) 12, 24, 36, 48, 60
6. 53, 59, 61, 67, 71, 73, 79, 83, 89, 97 1. (a) True (b) False (c) True (d) False (e) False
(f) True (g) True (h) False (i) True (j) False
7. 42, 44, 46, 48, 50, 52, 54, 56, 58 2. (b)
8. 1, 3, 5, 7, 9, 11, 13, 15, 17, 19
9. (a) 2 + 13 or 3 + 5 + 7 (b) 11 + 2 (c) 7 + 13 + 17 Practice Time
10. (a) 5 + 37 (b) 3 + 29 (c) 3 + 47 1. (a) 1, 3, 11, 33 (b) 1, 2, 11, 22 (c) 1, 2, 61, 122
(d) 1, 5, 7, 25, 35, 125
Exercise 4.2
1. (b) and (c) 2. (a) and (b) 3. (a) and (b) (e) 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 25, 30, 50, 60, 75,
100, 150, 300
4. (b) and (c) 5. (a) and (c) 6. (c)
7. (a) and (c) 8. (b) and (c) 9. (a) and (c) 2. Prime number: 3; Co-prime numbers: 3 and 112, 3 and 70,
15 and 112; Composite numbers: 12, 15, 70, 112
10. (a) 2 (b) 1 11. (a) 2 (b) 6 12. (a) 3 (b) 3
3. 23, 29, 31, 37
Exercise 4.3 4. (a) 6 (b) 7 (c) 15 (d) 8 (e) 20 (f) 20
1. (a) 1, 5 (b) 1, 2, 4 (c) 1, 7 (d) 1, 3 (e) 1, 2, 4 5. 9 6. 2
(f) 1, 3, 5, 15
2. (a) 24, 48, 72 (b) 18, 36, 54 (c) 50, 100, 150 7. (a) 13, 26, 39, 52 (b) 9, 18, 27, 36, 45
3. 30 and 60 (c) 15, 30, 45, 60, 75 (d) 8, 16, 24, 32, 40, 48
4. (a) and (b) 8. (a) 24 (b) 36 (c) 315 (d) 600 (e) 240 (f) 72
5. Common factors: 1, 2, 4; 9. 1,620 10. 1,086 11. (a) 254 (b) 245
Common multiples: 4, 8, 12, 16, 20 12. 19 13. 910 14. LCM = 525 ; HCF = 35
6. 56, 70, 84 15. HCF = 1; LCM = 27,750;
Exercise 4.4 HCF × LCM = 27,750 = 222 × 125
th
1. (a) 2 × 2 × 2 × 3 × 11 × 11 (b) 2 × 2 × 3 × 5 × 5 × 5 16. 2 groups 17. 45 customer
(c) 3 × 3 × 3 × 3 × 7 × 7 (d) 7 × 11 × 11 × 11 Think Smart
(e) 3 × 3 × 17 × 19 (f) 3 × 7 × 13 × 17 1. 51
2. 999; 3 × 3 × 3 × 37 2. (a) False; As all prime numbers other than 2 are odd
3. 10,000; 2 × 2 × 2 × 2 × 5 × 5 × 5 × 5 numbers and the product of 2 and any odd number is
4. 2 × 5 × 11 × 11 × 17 an even number.
5. (a) No; 60 = 2 × 2 × 3 × 5 (b) Yes (b) True; As for the given case the least possible prime
(c) No; 72 = 2 × 2 × 2 × 3 × 3 numbers are 3 and 5, and even their product, i.e.,
6. (a) 12 (b) 16 (c) 35 15, is more than 10.
4 3 4 4 5 7 (c) False; As an odd number is not completely divisible
by 2.
2 2 2 2 2 2
Chapter 5
(Answers may vary) Exercise 5.1
Exercise 4.5 1. (a) 12 (b) (c) (d) (e) 11 (f) 2
3
5
1
1. (a) 5 (b) 2 (c) 4 (d) 6 (e) 3 (f) 1 (g) 9 (h) 33 13 4 8 7 13 3
2. (a) 9 (b) 64 (c) 176 (d) 1 (e) 5 (f) 30 (g) 24 2. Proper: 3 11 5 Improper: 20 251 , 110
,
,
,
(h) 135 4 12 9 11 159 110
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