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Chapter: Arithmetic Progression· Mathematics Part 1 (Algebra)

Asked in: March 2026 board paperSachin invested some amount in a National Saving Certificate Scheme. In the first year he invested ₹ 5,000, in the second year ₹ 7,000, in the third year ₹ 9,000 and so on. Find the total amount that he invested in 12…

Asked in: March 2026 board paper

Sachin invested some amount in a National Saving Certificate Scheme. In the first year he invested ₹ 5,000, in the second year ₹ 7,000, in the third year ₹ 9,000 and so on. Find the total amount that he invested in 12 years.

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Answer: ₹ 1,92,000

The yearly amounts 5000, 7000, 9000, … form an A.P. with \(a = 5000\), \(d = 2000\), \(n = 12\).

\(S_n = \dfrac{n}{2}[2a + (n - 1)d]\)

\(S_{12} = \dfrac{12}{2}[2 \times 5000 + 11 \times 2000] = 6[10000 + 22000] = 6 \times 32000 = 192000\)

Total investment in 12 years = ₹ 1,92,000.

Doubtly AI · 29 Oct 2026 AI-verified · Nov 2026 Report
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