Answer:
202.8
Step-by-step explanation:
The geometric mean of 2 numbers a and b is
[tex]\sqrt{ab}[/tex]
Here a = 30 and mean = 78, thus
[tex]\sqrt{30b}[/tex] = 78
To clear the radical square both sides
([tex]\sqrt{30b}[/tex] )² = 78², that is
30b = 6084 ( divide both sides by 30 )
b = [tex]\frac{6084}{30}[/tex] = 202.8
