alleryWhat is the LCM of 7 and 21?
- 21
- 7
- 3
- 147
Show answer and solution
Correct answer: A. 21
21 is already a multiple of 7, so the smallest common multiple is 21.
RRB NTPC LCM and HCF — practice questions — page 2
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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Showing questions 31–60 of 62.
What is the LCM of 7 and 21?Read the answer and worked solution →What is the HCF of the consecutive numbers 14 and 15?Read the answer and worked solution →Two different prime numbers always have which HCF?Read the answer and worked solution →Taking highest prime powers, compute lcm(108, 144).Read the answer and worked solution →Which of these pairs of numbers is coprime?Read the answer and worked solution →Given that HCF(8, 12) = 4, what is the HCF of 80 and 120?Read the answer and worked solution →What is the smallest perfect square divisible by 12, 18 and 30?Read the answer and worked solution →Which number first shows up in both the 15 and 25 times tables?Read the answer and worked solution →When finding the HCF from prime factors, which factors are multiplied?Read the answer and worked solution →Which of these is NOT a common multiple of 12 and 18?Read the answer and worked solution →How many common divisors do 54 and 24 have?Read the answer and worked solution →In Euclid's original subtraction method for the HCF, the larger number is replaced by what?Read the answer and worked solution →Numbers are written as 2^3 x 3 and 2 x 3^2. What is their least common multiple?Read the answer and worked solution →A number increased by 7 is exactly divisible by 12, 16 and 24. What is the least such number?Read the answer and worked solution →Which term is another name for the greatest common divisor?Read the answer and worked solution →To reduce 42/56 to lowest terms, both parts are divided by which number?Read the answer and worked solution →What is 42/56 in lowest terms?Read the answer and worked solution →By the unique factorization theorem, a number above 1 splits into primes in how many ways, ignoring order?Read the answer and worked solution →What common denominator is the LCM of the denominators when adding 1/4 and 1/6?Read the answer and worked solution →If the HCF of 20 and 30 is 10, what is their LCM?Read the answer and worked solution →A pair has HCF 1 and product 221. Find the LCM.Read the answer and worked solution →In the Euclidean algorithm, the pair (a, b) is repeatedly replaced by which pair?Read the answer and worked solution →The GCD is associative. Which expression equals gcd(a, gcd(b, c))?Read the answer and worked solution →By definition, a multiple of any number is the product of that number andRead the answer and worked solution →Two positive integers are coprime or relatively prime if their GCD equalsRead the answer and worked solution →How is the least common multiple of a and b computed using their GCD?Read the answer and worked solution →For any positive integer a, what is the value of gcd(a, a)?Read the answer and worked solution →For a > b, common divisors of a and b are identical to common divisors of b andRead the answer and worked solution →RRB NTPC · Find LCM of Number PairsRead the answer and worked solution →Find the Highest Common Factor (HCF) of 24 and 36:Read the answer and worked solution →
Worked practice questions
What is the HCF of the consecutive numbers 14 and 15?
- 14
- 1
- 15
- 29
Show answer and solution
Correct answer: B. 1
Consecutive numbers share no divisor except 1, so they are coprime.
Two different prime numbers always have which HCF?
- 1
- 3
- 0
- 2
Show answer and solution
Correct answer: A. 1
A prime has only 1 and itself as divisors, so two different primes share only 1.
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