Question:
Find the 12th term from the end of the following arithmetic progressions:
(i) 3, 5, 7, 9, ... 201
(ii) 3, 8, 13, ..., 253
(iii) 1, 4, 7, 10, ..., 88
Solution:
(i) 3, 5, 7, 9...201
Consider the given progression with 201 as the first term and −2 as the common difference.
12th term from the end $=201+(12-1)(-2)=179$
(ii) 3, 8, 13...253
Consider the given progression with 253 as the first term and −5 as the common difference.
12th term from the end $=253+(12-1)(-5)=198$
(iii) 1, 4, 7, 10...88
Consider the given progression with 88 as the first term and −3 as the common difference.
12th term from the end $=88+(12-1)(-3)=55$