You can configure NumLock to work with Mac OS X version 10.10 (Yosemite), by following these steps:
- Launch the System Preferences application
- Click Security & Privacy
- Select Privacy tab
- Choose the Accessibility row
- Click the lock to make changes, and enter your administrator's name and password.
- Check the box next to NumLock
If you don't see NumLock in the list, you can add it by using the + button or simply drag the NumLock app icon (probably in your Applications folder) to the window under "Allow the apps below to control your computer."
Thanks to user Ruffjm for the guidance.