Well, it could be a few things.
First I would check what is running on the tablet. Anything that is running in the background is going to be draining data. I would uninstall anything you no longer use, and set things you only use sometimes to not load/start when the device is turned on. Also, be sure you reboot it regularly. Leave it on all the time will cause it to drain faster.
If you play games on it, especially graphic intensive ones, that will drain the battery fast as well.
You may want to also check it for malware, viruses, etc.
Lastly, if none of that helps, you can try replacing the battery, as it may be going. I know there are apps out there that can monitor the battery usage for all things going on, on the tablet. You...