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

Answer 1

(i) A.P. is 3, 5, 7, 9, ..... 201
12th term from end is $l-(n-1)d$ i.e.
= 201 -(12 - 1)2 = 179

(ii) A.P is 3, 8, 13, ..... 253
12th term from end is $l-(n-1)d$ i.e.
= 253 - (12 -1)5
= 253 - 55
= 198

(iii) A.P is 1, 4, 7, 10, ....., 88
12th term from end is $l-(n-1)d$
= 88 - (12 - 1)3
= 88 - 33
= 55