alleryIf the last term is l, the sum of the first n terms of an AP is:
A$S_n = n(a + l)$
B$S_n = \dfrac{n}{2}(a + l)$
C$S_n = \dfrac{n}{2}(a - l)$
D$S_n = \dfrac{n}{2}(a \times l)$
Answer & Solution
Correct answer: B. $S_n = \dfrac{n}{2}(a + l)$
Using the last term l: Sₙ = n/2 (a + l).
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