Which of the following is a pair of co-primes?
25 and 36
Two numbers are co-prime if their highest common factor (HCF) is 1.
\(25 = 5^2\) and \(36 = 2^2 \times 3^2\); they share no common prime factor, so \(\text{HCF}(25,36) = 1\).
\(44 = 2^2 \times 11\) and \(99 = 3^2 \times 11\) share the factor 11, so their HCF is 11, not co-prime.
\(27 = 3^3\) and \(36 = 2^2 \times 3^2\) share the factor 3, so they are not co-prime.
\(42 = 2 \times 3 \times 7\) and \(56 = 2^3 \times 7\) share factors 2 and 7, so they are not co-prime.
Hence, 25 and 36 form a pair of co-primes.
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Important Questions from LCM and HCF
The greatest three-digit number which is divisible by 14, 28, and 42 is:
What is the greatest number that will divide 209 and 347 leaving remainder 5 and 7 respectively?
A number is three times another number and their HCF is 8. What is the sum of the squares of the numbers?
The HCF of 2091, 3485 and 4879 is x. The sum of the digits of x is:
If three numbers are in ratio of 3 : 5 : 7 and their LCM is 2415, what is the difference between the second number and the first number?
