Number Series — Constant Ratio (Geometric Progression) Find the next number in the sequence: 4, 12, 36, 108, ?
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A144
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B216
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C304
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D324
Answer
Correct Answer: 324
Explanation
Introduction / Context:Here the growth is multiplicative with a constant ratio, a hallmark of a geometric progression. Identifying the multiplier gives the next term immediately.
Given Data / Assumptions:
- Series: 4, 12, 36, 108, ?
- Check the ratio between consecutive terms.
Concept / Approach:In a geometric progression, each term equals the previous term multiplied by a constant r. Determine r and apply once more to find the missing term.
Step-by-Step Solution:12 / 4 = 336 / 12 = 3108 / 36 = 3Common ratio r = 3Next term = 108 * 3 = 324
Verification / Alternative check:The ratio remains constant at 3 across all visible steps. Extending once yields 324, consistent with the pattern.
Why Other Options Are Wrong:
- 144, 216, 304: These are not equal to 108 * 3 and thus break the geometric rule.
Common Pitfalls:Mistaking additive patterns for multiplicative ones. Always check both differences and ratios in fast sequence analysis.
Final Answer:324