Question

Find the 17th term from the end of the ap1,6,11,16......211,216

Answer 1

First we write the app in the reverse form so,
The Ap is 216,211.........16,11,6,1
The first term of Ap is = 216
The common difference is = - 5
a17 = a+ (n-1) d
a17 = 216 + (17-1)-5
= 216 - 80
a17 = 136

Answer 2

Given AP 1,6,11,17,....211,216
Take ap on reverse order
New ap is
216,211,206,.....6,1
First term=a=216
Common difference=d=a2-a1=211-216=-5
nth term in ap =an=a+(n-1)d
a17=216+(17-1)(-5)
=216-16*5
=216-80
=136
Therefore
a17=136