Page 166 - Maths Skill - 6

164 Maths

Chapter - 3: Prime Time

Boot-up

A. 1. (ii) 2. (iii) 3. (ii) 4. (i) 5. (i) B. 1. 1 2. 15 3. 4 4. even 5. 2
C. 1. True 2. False 3. True 4. False 5. False

Exercise - 3.1

1. (i) 5(18 – 5) (ii) 45 ÷ (5 + 4) (iii) 90 ÷{(5 + 3) + 2} (iv) 2{(30 – 6) –3}
2. (i) 36 (ii) 100 (iii) 11.8 (iv) 104 3. (i) 2 (ii) 8 (iii) 7 (iv) 52
Exercise - 3.2

1. (i) False (ii) True (iii) True (iv) False (v) False (vi) False (vii) False (viii) False (ix) True
2. (i) 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60 (ii) 1, 2, 4, 8, 16 (iii) 1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 24, 36, 48, 72, 144
(iv) 1, 2, 4, 7, 8, 14, 28, 56 (v) 1, 3, 5, 15 (vi) 1, 2, 3, 4, 6, 9, 12, 18, 36
3. (i) odd (ii) even (iii) odd (iv) even (v) odd (vi) odd
4. (i) 9, 18, 27, 36, 45 (ii) 19, 38, 57, 76, 95 (iii) 25, 50, 75, 100, 125 (iv) 11, 22, 33, 44, 55 (v) 20, 40, 60, 80, 100
(vi) 12, 24, 36, 48, 60
5. Prime numbers: 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
Composite numbers: 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49
6. (i) 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96 (ii) 15, 30, 45, 60, 75, 90 7. yes, 9
8. (41, 43), (59, 61), (71, 73) 9. 9, 15, 21, 25, 27
10. (i) 24 = 11 + 13 = 17 + 7 = 19 + 5 (ii) 44 = 41 + 3 = 37 + 7 = 31 + 13
(iii) 76 = 73 + 3 (iv) 80 = 73 + 7 11. (i) 31 = 23 + 5 + 3 (ii) 61 = 53 + 5 + 3 (iii) 71 = 41 + 23 + 7 (iv) 35 = 23 + 7 + 5
= 71 + 5 = 67 + 13 = 19 + 7 + 5 = 43 + 13 + 5 = 37 + 31 + 3 = 17 + 11 + 7
= 59 + 17 = 61 + 19 = 17 + 11 + 3 = 43 + 11 + 7 = 29 + 23 + 19 = 19 + 13 + 3
= 53 + 23 = 43 + 37 = 13 + 11 + 7 = 41 + 17 + 3 = 47 + 17 + 7 = 17 + 13 + 5
= 47 + 29 = 37 + 19 + 5 = 43 + 23 + 5
= 31 + 17 + 13 = 41 + 17 + 13
= 29 + 19 + 13 = 31 + 29 + 11
12. No 13. 3, 13, 23, 43, 53, 73, 83 14. (i) (3, 5) (ii) (11, 13) (iii) (17, 19) (iv) (41, 43)

Exercise - 3.3

1. (i) True (ii) False (iii) True (iv) True (v) True (vi) False (vii) True
2. (i) 3, 6 and 9 (ii) 5 (iii) 3, 9 and 11 (iv) 3 and 6 (v) 3, 6 and 9 (vi) 5 and 10 (vii) 11 (viii) 11
3. (i) 2 and 4 (ii) 2, 4 and 8 (iii) 2 and 4 (iv) 2 (v) 2 (vi) 2 and 4
4. (i) 0 (ii) 2 (iii) 1 (iv) 0 (v) 0 (vi) 3 (vii) 2 (viii) 0, 0 (ix) 3

5. (ii) , (iii), (v) and (vii) 6. (i) 2, 3, 5, 7 and 11. Since 137 is not divisible by any of these numbers, so it is a prime number.
(ii) 2, 3, 5, 7, 11 and 13. Since 203 is divisible by 7, so it is not a prime number.
(iii) 2, 3, 5, 7, 11, 13 and 17. Since 317 is not divisible by any of these numbers, so it is a prime number.
(iv) 2, 3, 5, 7, 11, 13, 17 and 19. Since 407 is divisible by 11, so it is not a prime number.