Answer:
7.8
Step-by-step explanation:
Let the Geometric mean of 4 and 15 be x.
[tex] \therefore \: x = \sqrt{4 \times 15} \\ \hspace{20 pt }= \sqrt{60} \\ \hspace{20 pt }= 7.74596669 \\ \hspace{20 pt }= 7.8 \\ [/tex]
