Given $X$ and $Y$ and a percent, how do I calculate the quantity that is that percent between them? Here is a really dumb question, but I cannot find answers on Google for some reason or other.  All the answers seem to be buried under mounds of percent difference formulas (which is not what I am asking).
I am trying to generate a value between two variables based on a percentage.
$$\begin{align*}
0\% &= X \qquad \text{(the minimum value)}\\\\
50\% &= \frac{X + Y}{2}\\\\
100\% &= Y\qquad \text{(the maximum value)}
\end{align*}$$
What would the formula be?

The formula for "$t$ percent", where $t$ is any number between $0$ and $100$, is
$$\left(1-\frac{t}{100}\right)X+\left(\frac{t}{100}\right)Y$$
