Question

Find the 9th term from the end (towards the first term) of the AP 5,9,13,.....,185.

Answer 1

a = 5

d = 4

L = 185

L9 = L - 8d

= 185 - 8*4

= 185 - 32

= 153

Answer 2

rearrange the ap in descending order i.e begin from 185
now
a=185
D=-4
a9=a+8d
a9=185-32
a9=153