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16
8/(1−0.5).
Class 12 · English Medium · Pearson Edexcel · Mathematics
Ratio, proportion and algebra
Compare finite and convergent infinite sequences.
About this lesson and its coverage
Original Kidemy Class 12 progression. This level has its own text, examples and questions. Curriculum versions share the progression; complete board-specific coverage still needs specification matching and additional material.
Learn the idea
A geometric sum converges only when the ratio has magnitude below1. The sum to infinity is a/(1−r) under that condition. A finite sum is meaningful without convergence. Algebraic expressions should state whether the process ends.
Worked example
For a=6,r=1/3, the infinite sum is 9. For r=2 the growing partial sums do not approach a finite limit.
- Identify the quantities and restrictions.
- Show a method with units or symbols.
- Check and explain the result.
Your written practice
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40
1+3+9+27.
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210
20×21/2.
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Partial sums alternate rather than approach one limit.
Do not apply the infinite-sum formula outside its conditions.
Write in your own words. A guardian or teacher should review this response.
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C(4,2)×2²=6×4=24.
Use both the choice count and power of 2.
Progress and browser storage
Notebook challenge, sources and further study
Apply the idea
Compare partial sums for one convergent and one divergent example.
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- Use the stated evidence or givens.
- Show reasoning rather than only a result.
- Review and explain one correction.
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