Which of the following pairs of numbers is co-prime (shares no common factor other than 1)?
- A.(8, 9) ✓
- B.(6, 9)
- C.(4, 8)
- D.(9, 12)
Explanation: 8 = 2³ and 9 = 3² share no common factor besides 1, so they're co-prime. The other pairs all share a factor greater than 1.
Class 6 IMO Mathematics Olympiad practice · Number Sense · Factors, Multiples & Primes
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