10.) {The sum of first 41st term of an AP is 5125. Find 21st term.} 11. {The sum of the third and seventh term of an AP is 6 and their product is 8. Find the first term and common difference. }12.{ There is an auditorium with 35 rows of seats. There are 20 seats in first row, 22 seats in second row, 24 seats in third row and so on. Find the no. of seats in 25th row.
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10) 125
11) a = 1 and d = 1/2 or a = 5 or d = -1/2
12) 68 seats in 25th row
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