Question

what are real life applications of knowing how to combine different functions together?

Answer 1

anything that involves some type of input for some kind of output can be used as a function

Answer 2

what is an example of a real life application of combining functions?

Answer 3

well how about this, each player on a baseball gets so many hits per game.. and each individual player can have his own function... just to name a few, lets say
y=.3x
y=.25x
y=.350x
etc etc... where x are at bats and y are hits....
you can combine these functions to make one function for an entire team with so many x at bats and y hits.