Question

The sum of 1st 6 terms of an ap is 99 ?is 6th term is 39?
What is the sum of its 3rd and 4th term

Answer 1

Given,
sum of 1st 6 terms of an AP , S6= 99
6th term, t6 = 39........(1)
sum of 3rd and 4th term = ?

sum of 1st 6 terms of an AP = 99
use formula , $S_6=\frac{6}{2}[a+t_6]$
99 = 3(a + 39) [ from equation (1), ]
33 = a + 39
a = -6

so, 6th term , t6 = a + (6 - 1)d
39 = -6 + 5d
45 = 5d
d = 9

3rd term = a + 2d = -6 + 18 = 12
4th term = a + 3d = -6 + 27 = 21

hence, sum of 3rd and 4th term = 12 + 21
= 33

Answer 2

HEY MATE !


HERE'S YOUR ANSWER


ANSWER :-

33


EXPLAINATION :-

IN THE ATTACHMENT