Question

Which term of the ap 3 15 2739 will be 120 more than its 21st term?

Answer 1

Let the term be n

$</h2><h2>\begin{lgathered}Let\ the\ term\ be\ n^{th}\ term\ of\ the\ AP. \\ \\ \\ d = 15 - 3 = 12 \\ \\ \\ T_n - T_{21} = 120 \\ \\ = (n - 21)d = 120 \\ \\ = (n - 21)12 = 120 \\ \\ n - 21 = \frac{120}{12} = 10 \\ \\ n = 10 + 21 = \bold{31} \\ \\ \\\end{lgathered} </h2><h2>$

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