Olympiad Level â Very Tricky : āĻ
āϞāĻŋāĻŽā§āĻĒāĻŋāϝāĻŧāĻžāĻĄ āϏā§āϤ⧰ â āĻ
āϤāĻŋ āĻāĻāĻŋāϞ
61. Smallest number leaving remainder 2 when divided by 3 and 4: 3 āĻā§°ā§ 4-ā§°ā§ āĻšā§°āĻŖ āĻā§°āĻŋāϞ⧠2 āĻ
ā§ąāĻļāĻŋāώā§āĻ āĻĨāĻāĻž āϏ⧰ā§āϤāĻŽ āϏāĻāĻā§āϝāĻž āĻā§āύāĻā§ ?
Options: (a) 6 (b) 10 (c) 14 (d) 18
Ans: (c) 14
Explanation: The LCM of 3 and 4 is 12. Adding the remainder 2 gives 12 + 2 = 14. āĻŦā§āϝāĻžāĻā§āϝāĻž: 3 āĻā§°ā§ 4-ā§° āϞ.āϏāĻž.āĻā§. = 12āĨ¤ āĻ
ā§ąāĻļāĻŋāώā§āĻ 2 āϝā§āĻ āĻā§°āĻŋāϞ⧠12 + 2 = 14āĨ¤
62. HCF of co-prime numbers 14 and 25: āϏāĻšāĻŽā§āϞāĻŋāĻ āϏāĻāĻā§āϝāĻž 14 āĻā§°ā§ 25-ā§° āĻ.āϏāĻž.āĻā§. āĻāĻŋāĻŽāĻžāύ ?
Options: (a) 7 (b) 5 (c) 1 (d) 2
Ans: (c) 1
Explanation: Co-prime numbers always have HCF = 1 because they have no common factor other than 1.āĻŦā§āϝāĻžāĻā§āϝāĻž: āϏāĻšāĻŽā§āϞāĻŋāĻ āϏāĻāĻā§āϝāĻžā§° āĻ.āϏāĻž.āĻā§. āϏāĻĻāĻžāϝāĻŧ 1, āĻāĻžā§°āĻŖ āϏāĻŋāĻšāĻāϤ⧰ 1-ā§° āĻŦāĻžāĻšāĻŋā§°ā§ āĻāύ āĻā§āύ⧠āϏāĻžāϧāĻžā§°āĻŖ āĻā§āĻŖāύā§āϝāĻŧāĻ āύāĻžāĻĨāĻžāĻā§āĨ¤
63. Product of two numbers is 144 and HCF is 12. What is the LCM ? āĻĻā§āĻāĻž āϏāĻāĻā§āϝāĻžā§° āĻā§āĻŖāĻĢāϞ 144 āĻā§°ā§ āĻ.āϏāĻž.āĻā§. 12āĨ¤ āϞ.āϏāĻž.āĻā§. āĻāĻŋāĻŽāĻžāύ ?
Options: (a) 6 (b) 12 (c) 18 (d) 24
Ans: (b) 12
Explanation: Use the formula: Product = HCF × LCM (āĻŦā§āϝāĻžāĻā§āϝāĻž: āϏā§āϤā§ā§°: āĻā§āĻŖāĻĢāϞ = āĻ.āϏāĻž.āĻā§. × āϞ.āϏāĻž.āĻā§.)
So, āĻ
ā§°ā§āĻĨāĻžā§, 144 = 12 × LCM
LCM (āϞ.āϏāĻž.āĻā§.)= 144 ÷ 12 = 12
64. Which number has the greatest number of factors ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ā§° āĻā§āĻŖāύā§āϝāĻŧāĻā§° āϏāĻāĻā§āϝāĻž āϏ⧰ā§āĻŦāĻžāϧāĻŋāĻ ?
Options: (a) 18 (b) 19 (c) 23 (d) 29
Ans: (a) 18
Explanation:18 has factors 1,2,3,6,9,18 (6 factors); others are prime with only 2 factors.
65. Smallest 3-digit number divisible by 11: 11-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻāĻāĻžāĻāϤāĻā§ āϏ⧰⧠3 āĻ
āĻāĻā§° āϏāĻāĻā§āϝāĻž āĻā§āύāĻā§ ?
Options: (a) 100 (b) 110 (c) 121 (d) 132
Ans: (b) 110
Explanation: 11 × 10 = 110, the first 3-digit multiple.
66. If a number is divisible by 8, it must be divisible by: āĻāĻāĻž āϏāĻāĻā§āϝāĻž āϝāĻĻāĻŋ 8-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻšāϝāĻŧ, āϤā§āύā§āϤ⧠āϏā§āĻāĻā§ āύāĻŋāĻļā§āĻāĻŋāϤāĻāĻžā§ąā§ āĻāĻŋāĻšā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻš'āĻŦ ?
Options: (a) 2 (b) 4 (c) Both (d) None
Ans: (c) Both
Explanation: Since 8 = 2³, it is automatically divisible by 2 and 4.
67. Remainder when 500 is divided by 6: 500-āĻ 6-ā§°ā§ āĻšā§°āĻŖ āĻā§°āĻŋāϞ⧠āĻ
ā§ąāĻļāĻŋāώā§āĻ āĻāĻŋāĻŽāĻžāύ āĻš'āĻŦ ?
Options: (a) 1 (b) 2 (c) 3 (d) 4
Ans: (b) 2
Explanation: 6 × 83 = 498; remainder = 2.
68. Which is NOT a factor of 72 ? 72-ā§° āĻā§āĻŖāύā§āϝāĻŧāĻ āύāĻšāϝāĻŧ āĻā§āύāĻā§ ?
Options: (a) 6 (b) 8 (c) 9 (d) 10
Ans: (d) 10
Explanation: 72 is not divisible by 10.
69. Largest 2-digit prime: āĻāĻāĻžāĻāϤāĻā§ āĻĄāĻžāĻā§° ⧍ āĻ
āĻāĻā§° āĻŽā§āϞāĻŋāĻ āϏāĻāĻā§āϝāĻž āĻā§āύāĻā§ ?
Options: (a) 97 (b) 91 (c) 89 (d) 93
Ans: (a) 97
Explanation: 97 is prime; numbers after it (98, 99) are composite.
70. If two numbers are multiples of 6, their HCF is always: āϝāĻĻāĻŋ āĻĻā§āĻāĻž āϏāĻāĻā§āϝāĻž 6-ā§° āĻā§āĻŖāĻŋāϤāĻ āĻšāϝāĻŧ, āϤā§āύā§āϤ⧠āϏāĻŋāĻšāĻāϤ⧰ āĻ.āϏāĻž.āĻā§. āϏāĻĻāĻžāϝāĻŧ āĻāĻŋāĻŽāĻžāύ āĻš'āĻŦ ?
Options: (a) 6 (b) Multiple of 6 (c) 1 (d) 12
Ans: (b) Multiple of 6
Explanation: Both contain 6 as a factor, so HCF must include at least 6.
71. Which number is divisible by 99 ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ 99-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ ?
Options: (a) 198 (b) 297 (c) 396 (d) All
Ans: (d) All
Explanation: Each equals 99 × 2, 3, and 4 respectively.
72. Prime factorization of 100: 100-ā§° āĻŽā§āϞāĻŋāĻ āĻā§āĻŖāύā§āϝāĻŧāĻ āĻŦāĻŋāĻļā§āϞā§āώāĻŖ (Prime Factorization) āĻā§āύāĻā§ ?
Options: (a) 2²×5² (b) 4×25 (c) 10×10 (d) 20×5
Ans: (a) 2²×5²
Explanation: Only option written fully in prime factors.
73. Smallest number divisible by every number from 1–5: 1-ā§° āĻĒā§°āĻž 5āϞ⧠āĻĒā§ā§°āϤāĻŋāĻā§ āϏāĻāĻā§āϝāĻžā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻāĻāĻžāĻāϤāĻā§ āϏ⧰⧠āϏāĻāĻā§āϝāĻž āĻā§āύāĻā§ ?
Options: (a) 10 (b) 30 (c) 60 (d) 120
Ans: (c) 60
Explanation: LCM of 1,2,3,4,5 is 60.
74. Which number is divisible by 2,3,4,5,6 but NOT by 7 ? 2, 3, 4, 5 āĻā§°ā§ 6-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ, āĻāĻŋāύā§āϤ⧠7-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āύāĻšā§ā§ąāĻž āϏāĻāĻā§āϝāĻžāĻā§ āĻā§āύāĻā§ ?
Options: (a) 60 (b) 120 (c) 180 (d) 240
Ans: (a) 60
Explanation: 60 is divisible by all listed numbers except 7.
75. HCF of three consecutive numbers: āϤāĻŋāύāĻŋāĻāĻž āĻāĻā§ā§°āĻžāĻšā§ āĻĨāĻāĻž āϏāĻāĻā§āϝāĻžā§° āĻ.āϏāĻž.āĻā§. (HCF) āĻāĻŋāĻŽāĻžāύ ?
Options: (a) 1 (b) 2 (c) 3 (d) Depends
Ans: (a) 1
Explanation: Consecutive numbers share no common factor other than 1.
76. Which is the smallest square number divisible by 3 ? 3-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻāĻāĻžāĻāϤāĻā§ āϏ⧰⧠āĻĒā§ā§°ā§āĻŖāĻŦā§°ā§āĻ āϏāĻāĻā§āϝāĻž āĻā§āύāĻā§ ?
Options: (a) 3 (b) 6 (c) 9 (d) 12
Ans: (c) 9
Explanation: 3² = 9.
77. LCM of consecutive numbers 4 and 5: āĻāĻā§ā§°āĻžāĻšā§ āĻĨāĻāĻž āϏāĻāĻā§āϝāĻž 4 āĻā§°ā§ 5-ā§° āϞ.āϏāĻž.āĻā§. (LCM) āĻāĻŋāĻŽāĻžāύ ?
Options: (a) 10 (b) 15 (c) 20 (d) 25
Explanation: Co-prime numbers → LCM = product (4×5).
78. Which number leaves remainder 1 when divided by any number ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§āĻ āϝāĻŋāĻā§āύ⧠āϏāĻāĻā§āϝāĻžā§°ā§ āĻšā§°āĻŖ āĻā§°āĻŋāϞ⧠āϏāĻĻāĻžāϝāĻŧ āĻ
ā§ąāĻļāĻŋāώā§āĻ 1 āĻĨāĻžāĻā§ ?
Options: (a) 0 (b) 1 (c) Divisor+1 (d) Prime
Ans: (c) Divisor+1
Explanation: A number one more than the divisor always leaves remainder 1.
79. If a number is divisible by both 9 and 11, it is divisible by: āĻāĻāĻž āϏāĻāĻā§āϝāĻž āϝāĻĻāĻŋ 9 āĻā§°ā§ 11 āĻĻā§āϝāĻŧā§āĻāĻžā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻšāϝāĻŧ, āϤā§āύā§āϤ⧠āϏā§āĻāĻā§ āĻāĻŋāĻšā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻš'āĻŦ ?
Options: (a) 18 (b) 99 (c) 121 (d) 100
Ans: (b) 99
Explanation: 9 and 11 are co-prime → LCM = 99.
80. Number of factors of 49: 49-ā§° āĻŽā§āĻ āĻā§āĻŖāύā§āϝāĻŧāĻā§° āϏāĻāĻā§āϝāĻž āĻāĻŋāĻŽāĻžāύ ?
Options: (a) 2 (b) 3 (c) 4 (d) 5
Ans: (b) 3
Explanation: Factors are 1, 7, 49.
81. Greatest multiple of 15 less than 200: 200-āϤāĻā§ āϏ⧰⧠15-ā§° āĻāĻāĻžāĻāϤāĻā§ āĻĄāĻžāĻā§° āĻā§āĻŖāĻŋāϤāĻ āĻā§āύāĻā§ ?
Options: (a) 180 (b) 195 (c) 190 (d) 175
Ans: (b) 195
Explanation:15 × 13 = 195; next is 210 (>200).
82. Which is divisible by 12 ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ 12-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ ?
Options: (a) 144 (b) 150 (c) 152 (d) 154
Ans: (a) 144
Explanation: Divisible by both 3 and 4.
83. The HCF of identical numbers is: āĻāĻā§ āϏāĻāĻā§āϝāĻž āĻĻā§āĻāĻžā§° āĻ.āϏāĻž.āĻā§. (HCF) āĻāĻŋāĻŽāĻžāύ āĻšāϝāĻŧ ?
Options: (a) 1 (b) The number itself (c) 0 (d) Double
Ans: (b) The number itself
Explanation: Greatest common factor equals the number.
84. Which number is divisible by 15 ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ 15-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ ?
Options: (a) 45 (b) 46 (c) 47 (d) 48
Ans: (a) 45
Explanation: Must be divisible by 3 and 5.
85. How many factors does 1 have ? 1-ā§° āĻāĻŋāĻŽāĻžāύāĻāĻž āĻā§āĻŖāύā§āϝāĻŧāĻ āĻāĻā§ ?
Options: (a) 1 (b) 2 (c) 0 (d) Infinite
Ans: (a) 1
Explanation: Only divisor is 1 itself.
86. Which is the smallest cube number ? āĻāĻāĻžāĻāϤāĻā§ āϏ⧰⧠āĻĒā§ā§°ā§āĻŖāĻāύ āϏāĻāĻā§āϝāĻž (Cube Number) āĻā§āύāĻā§ ?
Options: (a) 1 (b) 2 (c) 4 (d) 8
Ans: (a) 1
Explanation: 1³ = 1.
87. If LCM is product, numbers are: āϝāĻĻāĻŋ āĻĻā§āĻāĻž āϏāĻāĻā§āϝāĻžā§° āϞ.āϏāĻž.āĻā§. (LCM) āϏāĻŋāĻšāĻāϤ⧰ āĻā§āĻŖāĻĢāϞ⧰ āϏāĻŽāĻžāύ āĻšāϝāĻŧ, āϤā§āύā§āϤ⧠āϏā§āĻ āϏāĻāĻā§āϝāĻž āĻĻā§āĻāĻž āĻāĻŋ ?
Options: (a) Equal (b) Co-prime (c) Even (d) Composite
Ans: (b) Co-prime
Explanation: Only co-prime numbers have LCM equal to their product.
88. Which is divisible by both 8 and 3 ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ 8 āĻā§°ā§ 3 āĻĻā§āϝāĻŧā§āĻāĻžā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ ?
Options: (a) 16 (b) 18 (c) 24 (d) 32
Ans: (c) 24
Explanation: LCM of 8 and 3 is 24.
89. Prime factors of 77: 77-ā§° āĻŽā§āϞāĻŋāĻ āĻā§āĻŖāύā§āϝāĻŧāĻāϏāĻŽā§āĻš (Prime Factors) āĻā§āύāĻŦā§ā§° ?
Options: (a) 7 (b) 11 (c) Both (d) 3
Ans: (c) Both
Explanation: 77 = 7 × 11.
90. Smallest multiple of 9: 9-ā§° āĻāĻāĻžāĻāϤāĻā§ āϏ⧰⧠āĻā§āĻŖāĻŋāϤāĻ āĻā§āύāĻā§ ?
Options: (a) 0 (b) 9 (c) 18 (d) 27
Ans: (a) 0
Explanation: 0 is a multiple of every number (9×0=0).
91. Which is NOT divisible by 5 ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ 5-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āύāĻšāϝāĻŧ ?
Options: (a) 115 (b) 125 (c) 132 (d) 145
Ans: (c) 132
Explanation: Numbers divisible by 5 end in 0 or 5.
92. Even number divisible by 3 must be divisible by: āĻāĻāĻž āϝā§āĻā§āĻŽ āϏāĻāĻā§āϝāĻž āϝāĻĻāĻŋ 3-ā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻšāϝāĻŧ, āϤā§āύā§āϤ⧠āϏā§āĻāĻā§ āύāĻŋāĻļā§āĻāĻŋāϤāĻāĻžā§ąā§ āĻāĻŋāĻšā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ āĻš'āĻŦ ?
Options: (a) 5 (b) 6 (c) 9 (d) 12
Ans: (b) 6
Explanation: Divisible by both 2 and 3 → divisible by 6
93. Smallest prime number: āĻāĻāĻžāĻāϤāĻā§ āϏ⧰⧠āĻŽā§āϞāĻŋāĻ āϏāĻāĻā§āϝāĻž āĻā§āύāĻā§ ?
Options: (a) 0 (b) 1 (c) 2 (d) 3
Ans: (c) 2
Explanation: Prime numbers start from 2.
94. Which number has only one factor ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ā§° āĻā§ā§ąāϞ āĻāĻāĻž āĻā§āĻŖāύā§āϝāĻŧāĻ āĻāĻā§ ?
Options: (a) 0 (b) 1 (c) 2 (d) 3
Ans: (b) 1
Explanation: 1 is neither prime nor composite.
95. LCM of same numbers is: āĻāĻā§ āϏāĻāĻā§āϝāĻžā§° āϞ.āϏāĻž.āĻā§. (LCM) āĻāĻŋāĻŽāĻžāύ āĻšāϝāĻŧ ?
Options: (a) 1 (b) Number itself (c) Double (d) Zero
Ans: (b) Number itself
Explanation: Least common multiple equals the number.
96. Which is a factor of all even numbers ? āϏāĻāϞ⧠āϝā§āĻā§āĻŽ āϏāĻāĻā§āϝāĻžā§° āĻā§āĻŖāύā§āϝāĻŧāĻ āĻā§āύāĻā§ ?
Options: (a) 1 (b) 2 (c) 3 (d) 5
Ans: (b) 2
Explanation: Every even number is divisible by 2.
97. Greatest factor of any number is: āϝāĻŋāĻā§āύ⧠āϏāĻāĻā§āϝāĻžā§° āĻāĻāĻžāĻāϤāĻā§ āĻĄāĻžāĻā§° āĻā§āĻŖāύā§āϝāĻŧāĻ āĻā§āύāĻā§ ?
Options: (a) 1 (b) Number itself (c) Half (d) Double
Ans: (b) Number itself
Explanation: A number always divides itself.
98. Which number is divisible by every number ? āĻā§āύ āϏāĻāĻā§āϝāĻžāĻā§ āϏāĻāϞ⧠āϏāĻāĻā§āϝāĻžā§°ā§ āĻŦāĻŋāĻāĻžāĻā§āϝ ?
Options: (a) 0 (b) 1 (c) 2 (d) 10
Ans: (a) 0
Explanation: 0 ÷ any non-zero number = 0.
99. How many multiples does a number have ? āĻāĻāĻž āϏāĻāĻā§āϝāĻžā§° āĻāĻŋāĻŽāĻžāύāĻāĻž āĻā§āĻŖāĻŋāϤāĻ (Multiples) āĻĨāĻžāĻā§ ?
Options: (a) Limited (b) Infinite (c) 10 (d) 100
Ans: (b) Infinite
Explanation: Multiples continue endlessly.
100. True statement:Options:(a) Every prime is odd(b) 2 is the only even prime(c) All odd numbers are prime(d) 1 is prime
Ans: (b) 2 is the only even prime
Explanation: Every even number except 2 has more than two factors.