Solution:

In the given G.P.

First term, \[a\text{ }=\text{ }-10\]

Common ratio, \[r\text{ }=\text{ }\left( 5/\surd 3 \right)/\text{ }\left( -10 \right)\text{ }=\text{ }1/\left( -2\surd 3 \right)\]

We know that, the general term is

\[{{t}_{n}}~=\text{ }a{{r}^{n\text{ }-\text{ }1}}\]

So,

\[{{t}_{n}}~=\text{ }\left( -10 \right){{\left( \text{ }1/\left( -2\surd 3 \right) \right)}^{n\text{ }-\text{ }1}}~=\text{ }-5/72\]

On equating the given equation,

\[n\text{ }-\text{ }1\text{ }=\text{ }4\]

\[n\text{ }=\text{ }5\]

Therefore, the \[~{{5}^{th}}\]of the given G.P. is \[-5/72\]