# How do you find a1 given an = 24, r = 2/3, n = 4?

Sep 26, 2016

This question is not clear about where the sequence is geometric or arithmetic.

The nth term of a geometric sequence is given by ${t}_{n} = a \times {r}^{n - 1}$.

$24 = a \times {\left(\frac{2}{3}\right)}^{4 - 1}$

$24 = a \times \frac{8}{27}$

$a = \frac{24}{\frac{8}{27}}$

$a = 81$

Hopefully this helps!