# For an A.P., If t1 = 1 and tn = 149 then find Sn. Activitry :- Here t1= 1, tn = 149, Sn = ? Sn = nn2(□+□) = nn2×□ = □ n, where n = 75 - Algebra

Sum

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

#### Solution

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

Concept: Sum of First n Terms of an AP
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