A: Life is simple here, just use command: which.
As an example, imagine you'd like to find out where the famous cp command is located, you'd run (included with the output in my case as well):
which cp /usr/bin/cpnow you know :)
This is really powerful mostly for those scripts with multiple versions present on the system. To ensure you use the correct one.
If interested in full power, check the man page: http://www.linuxmanpages.com/man1/which.1.php