alleryWhat is the HCF of 16, 72 and 28?
- 3
- 4
- 2
- 1
Show answer and solution
Correct answer: B. 4
1. 16 = 2^4, 72 = 2^3 x 3^2, 28 = 2^2 x 7.
2. The common prime factor is 2, lowest power 2^2 = 4.
3. So HCF = 4.
_Source: RRB Group D CEN-02/2018 PYQ, Q.25._
RRB NTPC LCM and HCF — practice questions
Explore 62 free LCM and HCF questions in RRB NTPC Mathematics. Open each question or exercise to read its content, reference answers and available explanation.
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What is the HCF of 16, 72 and 28?Read the answer and worked solution →The HCF of 156, 312 and 195 is:Read the answer and worked solution →The least common multiple (LCM) of 14, 42 and 77 is:Read the answer and worked solution →The HCF of 96 and 404 is 4. Their LCM is:Read the answer and worked solution →The LCM of 6, 72 and 120 is:Read the answer and worked solution →What is the HCF of 96 and 404?Read the answer and worked solution →The smallest number that is exactly divisible by every number from 1 to 10 is:Read the answer and worked solution →Find the smallest positive integer divisible by both 12 and 18.Read the answer and worked solution →Find the largest integer that divides both 36 and 48 without remainder.Read the answer and worked solution →The product of two numbers is 1080 and their HCF is 6. What is their LCM?Read the answer and worked solution →Two numbers have HCF 12 and LCM 144. One number is 48. What is the other?Read the answer and worked solution →Items are packed in boxes of 4, 6 or 8 with none left. What is the least total?Read the answer and worked solution →What is the largest number that divides both 60 and 84 exactly?Read the answer and worked solution →Bells ring every 12, 15 and 20 minutes and ring together at 9:00 AM. When will they next ring together?Read the answer and worked solution →What is the greatest number that divides 125 and 153 leaving remainders 5 and 3 respectively?Read the answer and worked solution →Two numbers are in the ratio 3:4 and their HCF is 5. What is their LCM?Read the answer and worked solution →Find the HCF when the numbers are 2^3 x 3^2 and 2^2 x 3^3 x 5.Read the answer and worked solution →Taking highest prime powers, what is the lcm of 2^3 x 3^2 and 2^2 x 3^3 x 5?Read the answer and worked solution →Numbers 7 and 9 share no factor beyond 1. What is the smallest number both divide?Read the answer and worked solution →Find the least common multiple of the three numbers 15, 20 and 25.Read the answer and worked solution →Which highest common factor do 18, 24 and 30 all share?Read the answer and worked solution →The smallest three-digit multiple of 6, 8 and 12 together is which?Read the answer and worked solution →Find the greatest three-digit multiple common to 6, 8 and 12.Read the answer and worked solution →A floor is 640 cm by 480 cm. What is the side of the largest square tile that fits exactly?Read the answer and worked solution →Three lights change every 48 s, 72 s and 108 s. After how many seconds do they change together again?Read the answer and worked solution →Given LCM 60 and HCF 5 for a pair, compute the product of the pair.Read the answer and worked solution →What is the greatest common divisor of 0 and 17?Read the answer and worked solution →Using Euclid's division method, what is the HCF of 252 and 105?Read the answer and worked solution →What is the smallest number divisible by every whole number from 1 to 10?Read the answer and worked solution →Two numbers have HCF 9. Which of these cannot be their LCM?Read the answer and worked solution →
Worked practice questions
The HCF of 156, 312 and 195 is:
- 3
- 39
- 78
- 13
Show answer and solution
Correct answer: B. 39
1. 156 = 2^2 x 3 x 13, 312 = 2^3 x 3 x 13, 195 = 3 x 5 x 13.
2. Common factors are 3 and 13.
3. HCF = 3 x 13 = 39.
_Source: RRB Group D CEN-02/2018 PYQ, Q.64._
The least common multiple (LCM) of 14, 42 and 77 is:
- 308
- 462
- 154
- 168
Show answer and solution
Correct answer: B. 462
1. Prime factorise: 14 = 2×7, 42 = 2×3×7, 77 = 7×11.
2. LCM takes the highest power of each prime: 2 × 3 × 7 × 11.
3. = 462.
_Source: RRB Group D CEN-02/2018 PYQ, Q.8._
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