4. For the geometric sequence $\left\{a_{n}\right\}$ with all terms being real numbers, the sum of the first $n$ terms is $S_{n}$. If $S_{10}=10, S_{30}=70$, then $S_{4 n}=$

Translate the above text into English, please retain the original text's line breaks and format, and output the translation result directly.
4. 150 Let the common ratio of the geometric sequence be $q$, then $S_{30}=\left(a_{1}+\cdots+a_{10}\right)+\left(a_{11}+\cdots+a_{20}\right)+\left(a_{21}+\cdots+a_{30}\right)=$ $S_{10}+S_{10} \cdot q^{10}+S_{10} \cdot q^{20} \Rightarrow q^{20}+q^{10}-6=0$, solving gives $q^{10}=2$ or -3 (discard), so $S_{40}=S_{30}+S_{10} \cdot q^{30}=$ $70+10 \times 8=150$