To close all background apps double tap the home button and a task bar will appear with icons of your most recently opened applications. Tap and hold your finger on any one of these until it wobbles and displays a red minus sign. Once it wobbles release your finger then proceed to tap the red minus sign on each icon until they are all gone. This does NOT delete your app but rather removes it from RAM entirely.
Once all background apps have been shut down tap the home button to return to your home screen.
Once on the home screen press and hold the power button located on the side of the iPad on the adjacent corner from your volume control until the power down slider appears on your screen. When it appears slide it over and the ipad will power down. You may observe a spinning wheel type icon in the middle of an otherwise black screen....this is normal and is an indication the iPad is performing a controlled shutdown.
Once powered down restart your iPad and see if,your problem has been remedied.