Central Exam — Quantitative Aptitude — HCF and LCM
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Showing 1–10 of 71 questions in HCF and LCM
Q.1 Medium HCF and LCM
Find the HCF and LCM of 36 and 48. What is their product?
A 1728
B 1440
C 1296
D 1680
Correct Answer:  A. 1728
Explanation:

36 = 2² × 3², 48 = 2⁴ × 3. HCF = 2² × 3 = 12, LCM = 2⁴ × 3² = 144.

Product = 36 × 48 = HCF × LCM = 12 × 144 = 1728.

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Q.2 Medium HCF and LCM
Two numbers have HCF of 8 and LCM of 96. If one number is 24, find the other number.
A 32
B 40
C 48
D 64
Correct Answer:  A. 32
Explanation:

Using formula: HCF × LCM = Product of two numbers. 8 × 96 = 24 × x. 768 = 24x. x = 32.

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Q.3 Medium HCF and LCM
What is the HCF of 100, 150, and 200?
A 25
B 50
C 75
D 100
Correct Answer:  B. 50
Explanation:

100 = 2² × 5², 150 = 2 × 3 × 5², 200 = 2³ × 5².

Common factors: 2¹ × 5² = 2 × 25 = 50.

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Q.4 Medium HCF and LCM
Find the LCM of 84 and 140.
A 420
B 840
C 210
D 280
Correct Answer:  A. 420
Explanation:

This question asks us to find the least common multiple (LCM) of two numbers using prime factorization.

Step 1: Find prime factorization of 84

Break 84 into its prime factors by dividing by smallest primes.

\[84 = 2^2 \times 3 \times 7\]
Step 2: Find prime factorization of 140

Break 140 into its prime factors by dividing by smallest primes.

\[140 = 2^2 \times 5 \times 7\]
Step 3: Calculate LCM using highest powers of all prime factors

LCM is found by taking the highest power of each prime factor that appears in either number.

\[\text{LCM} = 2^2 \times 3 \times 5 \times 7 = 4 \times 3 \times 5 \times 7 = 420\]

The LCM of 84 and 140 is 420, which is option (A).

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Q.5 Medium HCF and LCM
The HCF of two numbers is 15. If their LCM is 180, and one number is 45, find the other number.
A 45
B 60
C 75
D 90
Correct Answer:  B. 60
Explanation:

Using HCF × LCM = Product of two numbers: 15 × 180 = 45 × other number.

Therefore, other number = 2700 ÷ 45 = 60.

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Q.6 Medium HCF and LCM
What is the HCF of 144 and 196?
A 4
B 8
C 12
D 16
Correct Answer:  A. 4
Explanation:

144 = 2⁴ × 3². 196 = 2² × 7².

Common prime factors: 2².

Therefore, HCF = 4.

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Q.7 Medium HCF and LCM
Two numbers are in the ratio 4:5, and their HCF is 6. Find the larger number.
A 24
B 30
C 36
D 48
Correct Answer:  B. 30
Explanation:

Let numbers be 4k and 5k. HCF = k = 6.

Therefore, numbers are 24 and 30.

The larger number is 30.

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Q.8 Medium HCF and LCM
The HCF of 56, 84, and 140 is:
A 14
B 28
C 7
D 4
Correct Answer:  A. 14
Explanation:

56 = 2³ × 7, 84 = 2² × 3 × 7, 140 = 2² × 5 × 7.

Common prime factors: 2 × 7 = 14.

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Q.9 Medium HCF and LCM
What is the LCM of 16, 24, and 36?
A 72
B 108
C 144
D 216
Correct Answer:  C. 144
Explanation:

16 = 2⁴, 24 = 2³ × 3, 36 = 2² × 3². LCM = 2⁴ × 3² = 16 × 9 = 144.

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Q.10 Medium HCF and LCM
If the HCF of two numbers is 18 and their LCM is 324, one number is 36. The other number is:
A 162
B 180
C 196
D 216
Correct Answer:  A. 162
Explanation:

HCF × LCM = Product of numbers. 18 × 324 = 36 × other.

Therefore, other = 5832 ÷ 36 = 162.

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