Question

There are 6 lines. The 1st line has 9 people, 2nd line 11 people, 3rd 13 people.

how many people are in the 6th line? How many people are in the lines in total?

use arithmetic series to find how many people in 6th line
use finite series to find how many people in total

Answer 1

first term :9=a

common difference: 2 =d

A6=a+5d

=9+5(2)

=19

no of terms =9

`s{n} = (n)/(2) (a + an) \\ = (6)/(2) (9 + 19) \\ = 3(28) \\ = 84`