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Question
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
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Solution
Here, t1= 1, tn = 149, Sn = ?
Sn = \[\frac{n}{2} (\boxed{t_1} + \boxed{t_n})\]
= `n/2 (1 + 149)`
= \[\frac{n}{2} \times \boxed{150}\]
= \[\boxed{75}\] n, where n = 75
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