- ACo-prime numbers
- BTwin primes
- CComposite numbers
- DCommon multiples
Step-by-Step Solution
Two numbers having only 1 as a common factor are called co-prime (or relatively prime). Example: 8 and 9.
Answer: A) Co-prime numbers
Two numbers whose only common factor is 1 are called:
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Key idea: HCF and LCM — the two ends of common ground
**HCF** (Highest Common Factor) is the biggest number that divides both numbers — it sits at the *small* end of common factors. **LCM** (Least Common Multiple) is the smallest number both numbers divide — it sits at the *small* end of common multiples (which is the *big* side of factors). For Class 6, the simplest method is listing: write all the factors (or first several multiples) of each number and pick the right one. Faster methods come in Class 7.
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