- A9
- B12
- C6
- D4
Step-by-Step Solution
Factors of 18: 1, 2, 3, 6, 9, 18. Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24. The common ones are 1, 2, 3 and 6, so ? is 6 (it is also the HCF of 18 and 24). 9 divides only 18; 12 and 4 divide only 24.
Answer: C) 6
The Venn diagram sorts the factors of 18 and the factors of 24. One common factor is hidden by ?. Which number is it?
Class 6Playing with NumbersPlaying with Numbers
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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