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प्रश्न
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
उत्तर
Here, t1= 1, tn = 149, Sn = ?
Sn = `"n"/2 ("t"_1 + "t"_"n")`
= `"n"/2 (1 + 149)`
= `"n"/2 xx 150`
= 75 n, where n = 75
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