This is arithmetic progression based question from Chapter name- Arithmetic Progression

Chapter number- 9

Exercise – 9.4

In this question we have been given the arithmetic progression and we have to find the 12th term from the end of the arithmetic progressions: 3, 5, 7, 9, …. 201

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Understanding CBSE Mathematics

Class :- 10th

Question no 13 (i)

Given that,

A.P = 3, 5, 7, 9, …. 201

last term is 201

where, a = 3 and d = (5 – 3) = 2

an = 3 + (n – 1)2 = 201

3 + 2n – 2 = 201

2n = 200

n = 100

Hence the A.P has 100 terms.

therefore, the 12th term from the end is same as (100 – 12 + 1)th of the A.P which is the 89th term.

a

_{89}= 3 + (89 – 1)2= 3 + 88(2)

= 3 + 176 = 179

Hence, the 12th term from the end of the A.P is 179.