Question

The sum of 5th and 9 th terms of an AP is 30 if its 25th term is three times the 8th term find the AP

Answer 1

Hello Mate

In this AP

A+4d= 5th Term

A+8d= 9th Term

add both the term

2a+12d = 30

a+6d = 15

a+24d= 25th term

a+7d = 8t term

(a+7d)*3 = a+24d

3a + 21d = a+24d

2a = 3d

a= 3d/2

sub. in the first equation

3d/2 +6d = 15

3d +12d = 30

15d= 30

d= 2

so,

Ap= a +6(2)= 15

a= 15-12

a= 3

First AP

3 + 2 =5

a= 3, d= 2 First Ap = 5