JEE MainMathematicsSequences and SeriesMCQ+4 / −1
Suppose , .. be an arithmetic progression of natural numbers. If the ratio of the sum of first five terms to the sum of first nine terms of the progression is and , , then the sum of the first ten terms of the progression is equal to
- A290
- B380
- C460
- D510
View written solutionFree
Correct answer: B
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Let the arithmetic progression have first term and common difference .
Then the sum of first terms is
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Use the given ratio:
Now,
So,
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Cancel from both sides:
Cross-multiplying,
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Since all terms are natural numbers, take for some natural number .
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Now find :
Given so
Checking natural number values of :
- If , then (too small)
- If , then (fits)
- If , then (too large)
Hence,
Therefore,
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Now compute the sum of first 10 terms:
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Therefore, the required sum is
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Option check:
- A: ❌
- B: ✅
- C: ❌
- D: ❌
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