Which of the following gives the sum of the first terms of an arithmetic progression…

MATHEMATICS · Single correct · GCSE · Mathematics · Algebra · Algebra

Problem

Which of the following gives the sum

S_n

of the first

n

terms of an arithmetic progression whose first term is

a

and last term is

l

? (a)

S_n = \dfrac{n}{2}\,(l - a)

(b)

S_n = \dfrac{n}{2}\,(a + l)

(c)

S_n = n(a + l)

(d)

S_n = \dfrac{a + l}{2n}