Question

Find the sum of the arithmetic sequence. 5,7,9,11,...,23

Answer 1

Answer:

140

Step-by-step explanation:

The arithmetic series is 5, 7, 9, 11, ........., 23.

First u have to determine the no. of terms that can be done by using

Tₙ = [a + (n - 1)d]

Tₙ-------nth term

a---------first term

n---------no.of terms in the series

d---------common difference

here a = 5,d = 2.

let it contain n terms Tₙ= [a + (n-1)d]

Substitute Tₙ, a, and d in the equation

23 = 5 + (n - 1)2

Subtract 5 from each side.

18 = (n-1)2

Divide each side by 2

(n - 1) = 9

Add 1 to each side

n = 9 + 1 = 10

The sum of the arithmetic sequence formula: Sₙ= (n/2)[2a+(n-1)d]

Substitute Sₙ, a, n and d in the equation

Sₙ= (10/2)[2(5) + (10-1)2]

Sₙ= (5)[10 + (9)2]

Sₙ= 5[10 + 18]

Sₙ= 5[28] = 140

Therefore the sum of the arithmetic sequence is 140.