The mean proportional between $16$ and $49$ is:

The formula for the mean proportional between two numbers $a$ and $b$ is $\sqrt{ab}$.
Here, $a=16$ and $b=49$.
$$\text{Mean Proportional}=\sqrt{16\times 49}$$
$$\text{Mean Proportional}=\sqrt{16}\times \sqrt{49}=4\times 7=28$$