the sum of first 20 terms of an AP . is one third of the sum of next 20 terms. if first term is 1 find the sum of first 30 terms of this AP
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sum of first 30 terms is 900
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Let the first term be 1 and common difference be d.
★According to the question,
⠀⠀⠀
⠀⠀
Now,
⠀⠀━━━━━━━━━━━━━━━━━━━━━━━━━━━
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