Question

The 10th term from the end of an AP 7,10,13,......154,157 is

Answer 1

Answer:

apply these formula Sn= n/2(2a+l)

Answer 2

Given ,

The AP is 7 , 10 , 13 , .... , 154 , 157

Here ,

a = 7

l = 157

d = 3

We know that , the nth term of an AP from its end is given by

$\large \mathtt{ \fbox{ a_{n} = l - (n - 1)d}}$

Substitute the known values , we get

$\sf \hookrightarrow a_{n} = 157 - (10 - 1)3 \\ \\ \sf \hookrightarrow a_{n}= 157 - 27 \\ \\ \sf \hookrightarrow a_{n} = 130$

Hence , 130 is the 10th term from the end of an AP