Question

An arithmetic progression is such that the sum of the first 8 term is 156 And the sum of the first 10 term is 215. Find the fifth term

Answer 1

Answer:

The correct answer of this question is 41/2

Answer 2

Answer:

Step-by-step explanation:Here it goes,

We know :

Sn=n/2*[2a+(n-1)d],

so,

S8 =8/2[2a+(8-1)d]=156

=4[2a+7d]=156

=2a+7d=39......(1)

S10 =10/2[2a+(10-1)d]=215

=5[2a+9d]=215

=2a+9d=43.....(2)

Subtracting (1) from (2), we get:

2a+9d=43

- 2a+7d=39

= 2d=4

d = 2

Thus, common difference is d = 2.

Then, using either 1 or 2 we get First term or a = 12.5

So, we now know ;tn=a+(n-1)d

So, t5 = 12.5 + (5-1)2

= 12.5 + 8 = 20.5(ANSWER)

HOPE THIS HELPS.....