The mean proportional between 0.09 and 16 is:

The mean proportional between 0.09 and 16 is:

The mean proportional between $$\left(9 + 4\sqrt{5}\right) \text{ and } \left(18 - 8\sqrt{5}\right) \text{ is:}$$​

The ratio between the fourth proportional of 2, 8 and 12 to the mean proportional of 9 and 4 is:

The mean proportional between (18 + 10$$\sqrt{7}$$​) and (18 – 4$$\sqrt{7}$$​) is: