Question

The sum of the first term is 30, and the sum of the four terms from number of term 6 and number of term 9(inclusive)is 69. find the Arithmetical progression

Answer 1

Here first term of an A.P. a=30,. Let common difference be 'd'

According to question,

a+5d+a+6d+a+7d+a+8d=69

4a+26d= 69

4*30+ 26d=69

120 - 69 = - 26 d

51 = - 26 d

d = - 51/26

so 30, (30- 51/26), (30- 102/26), (30- 153/26)....... is required A.P.

30, 729/26 , 678/26, 627/26, ..............is your answer....