# How do you find the 10th term in the geometric sequence 320, 160, 80, 40, ...?

Nov 9, 2015

Geometric progression

#### Explanation:

320 , 160 , 80 , 40 , .....

First of all, you've to find the first term of the sequence,a,

first term, a =320

Then, you've to find the common ratio of the sequence.So,divide the second term with the first term,

common ratio, r = 160/320

$$                     r = 1/2


Use the formula ${T}_{n} = a \left({r}^{n - 1}\right)$

${T}_{10} = 320 \left[{\left(\frac{1}{2}\right)}^{9}\right]$

${T}_{10} = \frac{5}{8}$