# How do you find the term n=81, given the arithmetic sequence a_1=20 and d=4?

Nov 4, 2016

${81}^{s t}$ term of the arithmetic sequence is $340$.

#### Explanation:

${n}^{t h}$ term of an arithmetic sequence, whose first term is ${a}_{1}$ and common difference is $d$ is

${a}_{1} + \left(n - 1\right) \times d$

As we have ${a}_{1} = 20$ and common difference is $d = 4$

${81}^{s t}$ term of the arithmetic sequence is

$20 + \left(81 - 1\right) \times 4 = 20 + 80 \times 4 = 20 + 320 = 340$