Question

Find the sum of the first 27 terms

of the arithmetic sequence.
First, fill in the equation.
a₁
= 5 and a27
Sn = 2/(a₁ + an)
Sn
=
[?]
2
+
=
83

Answer 1

S₂₇ = 1188

Explanation:

using the given formula for
`S_(n)` , that is

`S_(n)` =
`(n)/(2)` (a₁ +
`a_(n)` )

with a₁ = 5 and
`a_(n)` = a₂₇ = 83 , then

S₂₇ =
`(27)/(2)` (5 + 83) = 13.5 × 88 = 1188