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प्रश्न
Write the formula of the sum of first n terms for an A.P.
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उत्तर
Sum of the first n terms is given by
Sn = `"n"/2[2"a" + ("n" - 1)"d"]`,
where a = first term,
d = common difference
OR
Sn = `"n"/2("t"_1 + "t"_"n")`,
where t1 = first term,
tn = last term
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Q.16
For an A.P., If t1 = 1 and tn = 149 then find Sn.
Activitry :- Here t1= 1, tn = 149, Sn = ?
Sn = `"n"/2 (square + square)`
= `"n"/2 xx square`
= `square` n, where n = 75
