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32
5+9×3.
Class 11 · Bangla Version · Mathematics
Ratio, proportion and algebra
Use arithmetic and geometric sequences to model repeated change.
About this lesson and its coverage
Original Kidemy Class 11 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
An arithmetic sequence adds a constant difference. A geometric sequence multiplies by a constant ratio. Their sums use different formulas; identify which structure is present before substituting. A recurring process also needs a clearly defined starting index.
Worked example
For a=3,d=4, the nth arithmetic term is 3+4(n−1). For a=2,r=3, the first 4 geometric terms total 2(3^4−1)/(3−1)=80.
- Identify the quantities and restrictions.
- Show a method with units or symbols.
- Check and explain the result.
Your written practice
Show your working on paper. Check your answer, then choose Next.
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48
3×2^4.
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25
1+3+5+7+9.
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Each pair has the same total a+last; the sum is n(a+last)/2.
Explain the factor n/2, including odd n by the doubled-list argument.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
Their exponents and number of growth periods differ.
Define time zero and the indexing.
Progress and browser storage
Notebook challenge, sources and further study
Apply the idea
Compare two saving sequences as fictional arithmetic models without treating them as financial advice.
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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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