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Twin primes are two primes that differ by 2, like 3 and 5. Which pair of twin primes lies between 40 and 50?

Class 6Playing with NumbersPlaying with Numbers
  • A41 and 43
  • B43 and 47
  • C45 and 47
  • D41 and 47

Step-by-Step Solution

The only primes between 40 and 50 are 41, 43 and 47, and just 41 and 43 differ by 2. The trap is 45 and 47: is composite, so that pair is not even a pair of primes. The remaining pairs differ by 4 and by 6.
Answer: A) 41 and 43

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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