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Which term of the A.P. 3, 15, 27, 39,.. will be 132 more than its 54th term?

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Which term of the A.P. 3, 15, 27, 39,.. will be 132 more than its 54th term?

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Given A.P. is 3, 15, 27, 39, …

first term, a = 3

common difference, d = a2 − a1 

= 15 − 3 = 12

We know that,

an = a+(n−1)d

a54 = a+(54−1)d

= 3 + (53)(12)

⇒ 3 + 636 = 639

a54 = 639

We have to find the term of this A.P. which is 132 more than a54, i.e.771.

Let nth term be 771.

an = a+(n−1)d

771 = 3+(n −1)12

768 = (n−1)12

(n −1) = 64

n = 65

Therefore, 65th term was 132 more than 54th term.

Or another method is;

Let nth term be 132 more than 54th term.

n = 54 + 132/2

= 54 + 11 = 65th term

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