Question

Which one of the following is a pair of co-prime numbers?

• A. (14, 35)
• B. (18, 25)
• C. (31, 93)
• D. (32, 62)

Hint:

Co-prime numbers need not both be prime; they only require no common factors other than 1.

Answer 1

The Correct Option is B

Step 1: Definition of co-prime numbers.
Two numbers are co-prime if their HCF is 1 (i.e., they have no common factor other than 1).

Step 2: Find HCF of each pair.
(14, 35) → HCF = 7
(18, 25) → HCF = 1
(31, 93) → HCF = 31
(32, 62) → HCF = 2

Step 3: Identify the co-prime pair.
Only (18, 25) has HCF = 1.

Step 4: Final answer.
Therefore, (18, 25) is a co-prime pair.