In an auditorium there are 20 seats in the first row, 22 seats in the second row, 24 seats in the third row, and so on. If there are 25 rows, find the number of seats in the last row and the total number of seats.

Q.3 (B)(ii) In an auditorium there are 20 seats in the first row, 22 seats in the second row, 24 seats in the third row, and so on. If there are 25 rows, find the number of seats in the last row and the total number of seats.

Doubtly AI Asked 27 Oct 2026 AI-generated · not yet verified ssc 10th Save WhatsApp Report

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Answer: Last row has 68 seats; total 1100 seats.

The numbers of seats 20, 22, 24, … form an A.P. with \(a = 20,\ d = 2,\ n = 25\).

\(t_{25} = a + 24d = 20 + 48 = 68\).

\(S_{25} = \dfrac{n}{2}(t_1 + t_{25}) = \dfrac{25}{2}(20 + 68) = \dfrac{25}{2} \times 88 = 25 \times 44 = 1100\).

Doubtly AI · 27 Oct 2026 AI-generated · not yet verified Report

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In an auditorium there are 20 seats in the first row, 22 seats in the second row, 24 seats in the third row, and so on. If there are 25 rows, find the number of seats in the last row and the total number of seats.

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