Find the mean proportional between 16 and 81.

Correct option is D

Given:

We are asked to find the mean proportional between 16 and 81.

Concept Used:
The mean proportional between two numbers a and b is the number x such that:

​$$\frac{a}{x} = \frac{x}{b}$$​

x $$= \sqrt{a \cdot b}$$​

Solution:
Given a = 16 and b = 81, we find the mean proportional x:

x =$$\sqrt{16 \times 81} = \sqrt{1296} = 36$$​