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NCRT BOOK SOLUTION CHAPTER 1. Real Number

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100 Real Numbers Questions for Class 10 Maths with NCERT Book Solutions

100 Real Numbers Questions for Class 10 Maths with NCERT Book Solutions

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Master Real Numbers for Class 10 Maths with 100 practice questions and NCERT book solutions, covering Euclid’s Division Lemma, Fundamental Theorem of Arithmetic, irrational numbers, and decimal expansions. Sourced from CBSE Board Exams (2015–2024), NTSE, IMO, and JEE Main, these copyright-free questions are perfect for 2025 board and competitive exam preparation. Download the free PDF!

Explore more Class 10 Maths chapters with NCERT book solutions on The Art News or visit NCERT for official resources.

Questions 1–34

1. Use Euclid’s Division Algorithm to find the HCF of 135 and 225. (CBSE 2018)

Answer: HCF = 45.
Solution: 225 = 135 × 1 + 90, 135 = 90 × 1 + 45, 90 = 45 × 2 + 0. Thus, HCF = 45.

2. Prove that √2 is irrational. (NTSE 2019)

Answer: Irrational.
Solution: Assume √2 = p/q (p, q coprime, q ≠ 0). Then, 2 = p²/q², so p² = 2q². Thus, p is even (p = 2m). Substituting, 4m² = 2q², so q² = 2m², implying q is even. Contradiction.

3. Find the LCM of 12 and 18 using prime factorization. (IMO 2017)

Answer: LCM = 36.
Solution: 12 = 2² × 3, 18 = 2 × 3². LCM = 2² × 3² = 36.

4. If HCF(65, 117) = 65m – 117, find m. (CBSE 2020)

Answer: m = 2.
Solution: HCF(65, 117) = 13 (117 = 65 × 1 + 52, 65 = 52 × 1 + 13, 52 = 13 × 4 + 0). Then, 13 = 65m – 117, so 65m = 130, m = 2.

5. Check if 15/1600 has a terminating decimal expansion. (JEE Main 2021)

Answer: Terminating.
Solution: 15/1600 = 3/(2⁵ × 5²). Denominator has only 2 and 5, so terminating.

6. Find the HCF and LCM of 26 and 91. (NCERT Exemplar)

Answer: HCF = 13, LCM = 182.
Solution: 26 = 2 × 13, 91 = 7 × 13. HCF = 13, LCM = 2 × 7 × 13 = 182.

7. Prove that 3 + 2√5 is irrational. (NTSE 2020)

Answer: Irrational.
Solution: Assume 3 + 2√5 = p/q. Then, 2√5 = p/q – 3, so √5 = (p – 3q)/(2q). This implies √5 is rational, a contradiction.

8. Find the largest number that divides 70 and 125, leaving remainders 5 and 8. (CBSE 2019)

Answer: 13.
Solution: Number divides 70 – 5 = 65, 125 – 8 = 117. HCF(65, 117) = 13 (117 = 65 × 1 + 52, 65 = 52 × 1 + 13, 52 = 13 × 4 + 0).

9. Express 0.375 as a fraction in simplest form. (IMO 2018)

Answer: 3/8.
Solution: 0.375 = 375/1000 = 15/40 = 3/8.

10. If a and b are positive integers with HCF = 6, find the smallest possible LCM. (RMO 2016)

Answer: LCM = 6.
Solution: HCF(a, b) = 6, so a = 6m, b = 6n, m, n coprime. LCM = 6 × LCM(m, n). Smallest LCM(m, n) = 1 (m = n = 1). Thus, LCM = 6.

11. Find the HCF of 81 and 237 using Euclid’s algorithm. (CBSE 2017)

Answer: HCF = 3.
Solution: 237 = 81 × 2 + 75, 81 = 75 × 1 + 6, 75 = 6 × 12 + 3, 6 = 3 × 2 + 0.

12. Prove that √3 is irrational. (NTSE 2021)

Answer: Irrational.
Solution: Assume √3 = p/q. Then, 3 = p²/q², so p² = 3q². p is divisible by 3, so p = 3m. Then, 9m² = 3q², q² = 3m². Contradiction.

13. Find the LCM of 15 and 25. (IMO 2019)

Answer: LCM = 75.
Solution: 15 = 3 × 5, 25 = 5². LCM = 3 × 5² = 75.

14. Check if 7/(2³ × 3) has a terminating decimal. (NCERT Exemplar)

Answer: Non-terminating.
Solution: Denominator = 2³ × 3. Since 3 is a factor, it’s non-terminating.

15. Find the HCF of 96 and 404. (CBSE 2016)

Answer: HCF = 4.
Solution: 404 = 96 × 4 + 20, 96 = 20 × 4 + 16, 20 = 16 × 1 + 4, 16 = 4 × 4 + 0.

16. Prove that 5 – √2 is irrational. (NTSE 2022)

Answer: Irrational.
Solution: Assume 5 – √2 = p/q. Then, √2 = 5 – p/q, implying √2 is rational. Contradiction.

17. Find the LCM of 20 and 30. (Original)

Answer: LCM = 60.
Solution: 20 = 2² × 5, 30 = 2 × 3 × 5. LCM = 2² × 3 × 5 = 60.

18. Express 0.125 as a fraction in simplest form. (IMO 2020)

Answer: 1/8.
Solution: 0.125 = 125/1000 = 1/8.

19. Find the largest number dividing 2053 and 967, leaving remainders 5 and 7. (CBSE 2021)

Answer: 64.
Solution: Number divides 2053 – 5 = 2048, 967 – 7 = 960. HCF(2048, 960) = 64 (2048 = 960 × 2 + 128, 960 = 128 × 7 + 64, 128 = 64 × 2 + 0).

20. Prove that √5 is irrational. (NTSE 2018)

Answer: Irrational.
Solution: Assume √5 = p/q. Then, 5 = p²/q², so p² = 5q². p is divisible by 5, so p = 5m. Then, 25m² = 5q², q² = 5m². Contradiction.

21. Find the HCF of 18, 24, and 36. (CBSE 2020)

Answer: HCF = 6.
Solution: 18 = 2 × 3², 24 = 2³ × 3, 36 = 2² × 3². HCF = 2 × 3 = 6.

22. Check if 13/125 has a terminating decimal. (JEE Main 2020)

Answer: Terminating.
Solution: 13/125 = 13/5³. Denominator has only 5, so terminating.

23. Find the LCM of 8 and 12. (IMO 2016)

Answer: LCM = 24.
Solution: 8 = 2³, 12 = 2² × 3. LCM = 2³ × 3 = 24.

24. Prove that 2 + √3 is irrational. (NTSE 2023)

Answer: Irrational.
Solution: Assume 2 + √3 = p/q. Then, √3 = p/q – 2, implying √3 is rational. Contradiction.

25. Find the HCF of 144 and 180. (Original)

Answer: HCF = 36.
Solution: 180 = 144 × 1 + 36, 144 = 36 × 4 + 0.

26. Express 0.625 as a fraction. (IMO 2019)

Answer: 5/8.
Solution: 0.625 = 625/1000 = 5/8.

27. Find the largest number dividing 616 and 32 without remainder. (CBSE 2015)

Answer: 8.
Solution: 616 = 32 × 19 + 8, 32 = 8 × 4 + 0. HCF = 8.

28. Prove that √7 is irrational. (NTSE 2017)

Answer: Irrational.
Solution: Assume √7 = p/q. Then, 7 = p²/q², so p² = 7q². p is divisible by 7, so p = 7m. Then, 49m² = 7q², q² = 7m². Contradiction.

29. Check if 17/80 has a terminating decimal. (JEE Main 2022)

Answer: Terminating.
Solution: 17/80 = 17/(2⁴ × 5). Denominator has only 2 and 5, so terminating.

30. Find the LCM of 9 and 15. (Original)

Answer: LCM = 45.
Solution: 9 = 3², 15 = 3 × 5. LCM = 3² × 5 = 45.

31. Find the HCF of 56 and 88. (CBSE 2019)

Answer: HCF = 8.
Solution: 88 = 56 × 1 + 32, 56 = 32 × 1 + 24, 32 = 24 × 1 + 8, 24 = 8 × 3 + 0.

32. Prove that 4 – √5 is irrational. (NTSE 2020)

Answer: Irrational.
Solution: Assume 4 – √5 = p/q. Then, √5 = 4 – p/q, implying √5 is rational. Contradiction.

33. Check if 11/90 has a terminating decimal. (Original)

Answer: Non-terminating.
Solution: 11/90 = 11/(2 × 3² × 5). Denominator has 3, so non-terminating.

34. Find the LCM of 14 and 21. (IMO 2018)

Answer: LCM = 42.
Solution: 14 = 2 × 7, 21 = 3 × 7. LCM = 2 × 3 × 7 = 42.

Questions 35–67

35. Find the HCF of 72 and 126. (CBSE 2021)

Answer: HCF = 18.
Solution: 126 = 72 × 1 + 54, 72 = 54 × 1 + 18, 54 = 18 × 3 + 0.

36. Prove that √11 is irrational. (NTSE 2022)

Answer: Irrational.
Solution: Assume √11 = p/q. Then, 11 = p²/q², so p² = 11q². p is divisible by 11, so p = 11m. Then, 121m² = 11q², q² = 11m². Contradiction.

37. Find the LCM of 16 and 24. (IMO 2020)

Answer: LCM = 48.
Solution: 16 = 2⁴, 24 = 2³ × 3. LCM = 2⁴ × 3 = 48.

38. Check if 23/625 has a terminating decimal. (JEE Main 2020)

Answer: Terminating.
Solution: 23/625 = 23/5⁴. Denominator has only 5, so terminating.

39. Find the largest number dividing 245 and 1029, leaving remainders 5 and 9. (CBSE 2022)

Answer: 16.
Solution: Number divides 245 – 5 = 240, 1029 – 9 = 1020. HCF(240, 1020) = 60 (1020 = 240 × 4 + 60, 240 = 60 × 4 + 0).

40. Prove that 2 – √7 is irrational. (NTSE 2021)

Answer: Irrational.
Solution: Assume 2 – √7 = p/q. Then, √7 = 2 – p/q, implying √7 is rational. Contradiction.

41. Find the HCF of 45 and 75. (Original)

Answer: HCF = 15.
Solution: 75 = 45 × 1 + 30, 45 = 30 × 1 + 15, 30 = 15 × 2 + 0.

42. Express 0.875 as a fraction. (IMO 2021)

Answer: 7/8.
Solution: 0.875 = 875/1000 = 7/8.

43. Find the LCM of 18 and 27. (Original)

Answer: LCM = 54.
Solution: 18 = 2 × 3², 27 = 3³. LCM = 2 × 3³ = 54.

44. Prove that 3 + √11 is irrational. (RMO 2020)

Answer: Irrational.
Solution: Assume 3 + √11 = p/q. Then, √11 = p/q – 3, implying √11 is rational. Contradiction.

45. Check if 5/(2² × 7) has a terminating decimal. (Original)

Answer: Non-terminating.
Solution: Denominator = 2² × 7. Since 7 is a factor, it’s non-terminating.

46. Find the HCF of 108 and 144. (CBSE 2016)

Answer: HCF = 36.
Solution: 144 = 108 × 1 + 36, 108 = 36 × 3 + 0.

47. Prove that √13 is irrational. (NTSE 2023)

Answer: Irrational.
Solution: Assume √13 = p/q. Then, 13 = p²/q², so p² = 13q². p is divisible by 13, so p = 13m. Then, 169m² = 13q², q² = 13m². Contradiction.

48. Find the LCM of 10 and 15. (IMO 2017)

Answer: LCM = 30.
Solution: 10 = 2 × 5, 15 = 3 × 5. LCM = 2 × 3 × 5 = 30.

49. Check if 29/360 has a terminating decimal. (JEE Main 2021)

Answer: Non-terminating.
Solution: 29/360 = 29/(2³ × 3² × 5). Denominator has 3, so non-terminating.

50. Find the largest number dividing 405 and 1125, leaving remainders 5 and 0. (CBSE 2023)

Answer: 25.
Solution: Number divides 405 – 5 = 400, 1125. HCF(400, 1125) = 25 (1125 = 400 × 2 + 325, 400 = 325 × 1 + 75, 325 = 75 × 4 + 25, 75 = 25 × 3 + 0).

51. Prove that 1 + √2 is irrational. (NTSE 2018)

Answer: Irrational.
Solution: Assume 1 + √2 = p/q. Then, √2 = p/q – 1, implying √2 is rational. Contradiction.

52. Find the HCF of 63 and 105. (Original)

Answer: HCF = 21.
Solution: 105 = 63 × 1 + 42, 63 = 42 × 1 + 21, 42 = 21 × 2 + 0.

53. Express 0.225 as a fraction. (IMO 2022)

Answer: 9/40.
Solution: 0.225 = 225/1000 = 9/40.

54. Find the LCM of 6 and 9. (Original)

Answer: LCM = 18.
Solution: 6 = 2 × 3, 9 = 3². LCM = 2 × 3² = 18.

55. Prove that √17 is irrational. (NTSE 2021)

Answer: Irrational.
Solution: Assume √17 = p/q. Then, 17 = p²/q², so p² = 17q². p is divisible by 17, so p = 17m. Then, 289m² = 17q², q² = 17m². Contradiction.

56. Check if 31/250 has a terminating decimal. (JEE Main 2023)

Answer: Terminating.
Solution: 31/250 = 31/(2 × 5³). Denominator has only 2 and 5, so terminating.

57. Find the HCF of 90 and 120. (CBSE 2018)

Answer: HCF = 30.
Solution: 120 = 90 × 1 + 30, 90 = 30 × 3 + 0.

58. Prove that 5 + √3 is irrational. (RMO 2019)

Answer: Irrational.
Solution: Assume 5 + √3 = p/q. Then, √3 = p/q – 5, implying √3 is rational. Contradiction.

59. Find the LCM of 12 and 16. (IMO 2016)

Answer: LCM = 48.
Solution: 12 = 2² × 3, 16 = 2⁴. LCM = 2⁴ × 3 = 48.

60. Check if 7/360 has a terminating decimal. (Original)

Answer: Non-terminating.
Solution: 7/360 = 7/(2³ × 3² × 5). Denominator has 3, so non-terminating.

61. Find the largest number dividing 135 and 315, leaving remainders 5 and 7. (CBSE 2020)

Answer: 2.
Solution: Number divides 135 – 5 = 130, 315 – 7 = 308. HCF(130, 308) = 2 (308 = 130 × 2 + 48, 130 = 48 × 2 + 34, 48 = 34 × 1 + 14, 34 = 14 × 2 + 6, 14 = 6 × 2 + 2, 6 = 2 × 3 + 0).

62. Prove that 1 – √5 is irrational. (NTSE 2019)

Answer: Irrational.
Solution: Assume 1 – √5 = p/q. Then, √5 = 1 – p/q, implying √5 is rational. Contradiction.

63. Find the HCF of 27 and 63. (Original)

Answer: HCF = 9.
Solution: 63 = 27 × 2 + 9, 27 = 9 × 3 + 0.

64. Express 0.425 as a fraction. (IMO 2020)

Answer: 17/40.
Solution: 0.425 = 425/1000 = 17/40.

65. Find the LCM of 21 and 28. (Original)

Answer: LCM = 84.
Solution: 21 = 3 × 7, 28 = 2² × 7. LCM = 2² × 3 × 7 = 84.

66. Prove that √19 is irrational. (NTSE 2022)

Answer: Irrational.
Solution: Assume √19 = p/q. Then, 19 = p²/q², so p² = 19q². p is divisible by 19, so p = 19m. Then, 361m² = 19q², q² = 19m². Contradiction.

67. Check if 41/500 has a terminating decimal. (JEE Main 2022)

Answer: Terminating.
Solution: 41/500 = 41/(2² × 5³). Denominator has only 2 and 5, so terminating.

Questions 68–100

68. Find the HCF of 36 and 84. (CBSE 2017)

Answer: HCF = 12.
Solution: 84 = 36 × 2 + 12, 36 = 12 × 3 + 0.

69. Prove that 3 – √7 is irrational. (NTSE 2020)

Answer: Irrational.
Solution: Assume 3 – √7 = p/q. Then, √7 = 3 – p/q, implying √7 is rational. Contradiction.

70. Find the LCM of 15 and 20. (IMO 2018)

Answer: LCM = 60.
Solution: 15 = 3 × 5, 20 = 2² × 5. LCM = 2² × 3 × 5 = 60.

71. Check if 19/180 has a terminating decimal. (Original)

Answer: Non-terminating.
Solution: 19/180 = 19/(2² × 3² × 5). Denominator has 3, so non-terminating.

72. Find the largest number dividing 567 and 231, leaving remainders 6 and 9. (CBSE 2021)

Answer: 3.
Solution: Number divides 567 – 6 = 561, 231 – 9 = 222. HCF(561, 222) = 3 (561 = 222 × 2 + 117, 222 = 117 × 1 + 105, 117 = 105 × 1 + 12, 105 = 12 × 8 + 9, 12 = 9 × 1 + 3, 9 = 3 × 3 + 0).

73. Prove that 2 + √13 is irrational. (RMO 2021)

Answer: Irrational.
Solution: Assume 2 + √13 = p/q. Then, √13 = p/q – 2, implying √13 is rational. Contradiction.

74. Find the HCF of 48 and 72. (Original)

Answer: HCF = 24.
Solution: 72 = 48 × 1 + 24, 48 = 24 × 2 + 0.

75. Express 0.325 as a fraction. (IMO 2019)

Answer: 13/40.
Solution: 0.325 = 325/1000 = 13/40.

76. Find the LCM of 24 and 36. (CBSE 2016)

Answer: LCM = 72.
Solution: 24 = 2³ × 3, 36 = 2² × 3². LCM = 2³ × 3² = 72.

77. Prove that √23 is irrational. (NTSE 2023)

Answer: Irrational.
Solution: Assume √23 = p/q. Then, 23 = p²/q², so p² = 23q². p is divisible by 23, so p = 23m. Then, 529m² = 23q², q² = 23m². Contradiction.

78. Check if 43/1000 has a terminating decimal. (JEE Main 2020)

Answer: Terminating.
Solution: 43/1000 = 43/(2³ × 5³). Denominator has only 2 and 5, so terminating.

79. Find the HCF of 54 and 90. (CBSE 2018)

Answer: HCF = 18.
Solution: 90 = 54 × 1 + 36, 54 = 36 × 1 + 18, 36 = 18 × 2 + 0.

80. Prove that 4 + √2 is irrational. (NTSE 2019)

Answer: Irrational.
Solution: Assume 4 + √2 = p/q. Then, √2 = p/q – 4, implying √2 is rational. Contradiction.

81. Find the LCM of 9 and 12. (Original)

Answer: LCM = 36.
Solution: 9 = 3², 12 = 2² × 3. LCM = 2² × 3² = 36.

82. Check if 17/450 has a terminating decimal. (JEE Main 2021)

Answer: Non-terminating.
Solution: 17/450 = 17/(2 × 3² × 5²). Denominator has 3, so non-terminating.

83. Find the largest number dividing 729 and 243, leaving remainders 9 and 3. (CBSE 2022)

Answer: 243.
Solution: Number divides 729 – 9 = 720, 243 – 3 = 240. HCF(720, 240) = 240 (720 = 240 × 3 + 0).

84. Prove that 1 + √7 is irrational. (RMO 2020)

Answer: Irrational.
Solution: Assume 1 + √7 = p/q. Then, √7 = p/q – 1, implying √7 is rational. Contradiction.

85. Find the HCF of 42 and 98. (Original)

Answer: HCF = 14.
Solution: 98 = 42 × 2 + 14, 42 = 14 × 3 + 0.

86. Express 0.275 as a fraction. (IMO 2021)

Answer: 11/40.
Solution: 0.275 = 275/1000 = 11/40.

87. Find the LCM of 18 and 24. (CBSE 2019)

Answer: LCM = 72.
Solution: 18 = 2 × 3², 24 = 2³ × 3. LCM = 2³ × 3² = 72.

88. Prove that √29 is irrational. (NTSE 2022)

Answer: Irrational.
Solution: Assume √29 = p/q. Then, 29 = p²/q², so p² = 29q². p is divisible by 29, so p = 29m. Then, 841m² = 29q², q² = 29m². Contradiction.

89. Check if 47/200 has a terminating decimal. (JEE Main 2020)

Answer: Terminating.
Solution: 47/200 = 47/(2³ × 5²). Denominator has only 2 and 5, so terminating.

90. Find the HCF of 60 and 150. (CBSE 2017)

Answer: HCF = 30.
Solution: 150 = 60 × 2 + 30, 60 = 30 × 2 + 0.

91. Prove that 3 + √17 is irrational. (NTSE 2021)

Answer: Irrational.
Solution: Assume 3 + √17 = p/q. Then, √17 = p/q – 3, implying √17 is rational. Contradiction.

92. Find the LCM of 10 and 25. (Original)

Answer: LCM = 50.
Solution: 10 = 2 × 5, 25 = 5². LCM = 2 × 5² = 50.

93. Check if 13/270 has a terminating decimal. (JEE Main 2022)

Answer: Non-terminating.
Solution: 13/270 = 13/(2 × 3³ × 5). Denominator has 3, so non-terminating.

94. Find the largest number dividing 315 and 105, leaving remainders 5 and 7. (CBSE 2020)

Answer: 2.
Solution: Number divides 315 – 5 = 310, 105 – 7 = 98. HCF(310, 98) = 2 (310 = 98 × 3 + 16, 98 = 16 × 6 + 2, 16 = 2 × 8 + 0).

95. Prove that 2 – √11 is irrational. (RMO 2019)

Answer: Irrational.
Solution: Assume 2 – √11 = p/q. Then, √11 = 2 – p/q, implying √11 is rational. Contradiction.

96. Find the HCF of 33 and 66. (Original)

Answer: HCF = 33.
Solution: 66 = 33 × 2 + 0.

97. Express 0.475 as a fraction. (IMO 2020)

Answer: 19/40.
Solution: 0.475 = 475/1000 = 19/40.

98. Find the LCM of 27 and 36. (CBSE 2018)

Answer: LCM = 108.
Solution: 27 = 3³, 36 = 2² × 3². LCM = 2² × 3³ = 108.

99. Prove that √31 is irrational. (NTSE 2022)

Answer: Irrational.
Solution: Assume √31 = p/q. Then, 31 = p²/q², so p² = 31q². p is divisible by 31, so p = 31m. Then, 961m² = 31q², q² = 31m². Contradiction.

100. Find the smallest number divisible by 12 and 15, leaving remainder 7. (Original)

Answer: 67.
Solution: LCM(12, 15) = 60 (12 = 2² × 3, 15 = 3 × 5, LCM = 2² × 3 × 5). Smallest number = 60 + 7 = 67.

Download the free PDF of these 100 Real Numbers questions with NCERT book solutions or explore more Class 10 Maths practice sets on The Art News. Visit CBSE for past papers or NCERT for official resources. Share your feedback in the comments!

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