To find $f(40)$ using the function $f(x) = \frac{9}{5}x + 32$, substitute $x = 40$ into the equation:

$f(40) = \frac{9}{5}(40) + 32$

Now, calculate:

$f(40) = \frac{9 \times 40}{5} + 32 = \frac{360}{5} + 32 = 72 + 32 = 104$

So, $f(40) = 104$.

Would you like more details or have any questions?

Here are five related questions you can explore:

1. What is the slope of the function $f(x) = \frac{9}{5}x + 32$?
2. How would you find the inverse of the function $f(x) = \frac{9}{5}x + 32$?
3. What is the $y$-intercept of the function $f(x) = \frac{9}{5}x + 32$?
4. How would the graph of $f(x)$ change if the slope was doubled?
5. What is the domain and range of this linear function?

Tip: Linear functions like $f(x) = \frac{9}{5}x + 32$ always produce a straight line when graphed, and the slope tells you how steep that line is.