Voila!! Works.
Amazing how many programs are "open"!!
Just for clarification, not all the apps in the multitask bar are open. The multitask bar is a never ending list of every app you've opened. While the most recent are probably still in RAM (up to about 20 moderate sized apps on the 3rd gen iPad, fewer on earlier models) most of them will not be running. The iPad will automatically remove apps from RAM as it needs space.
Some apps like GPS navigation and music apps
may have some background tasks running. There are only a few types and methods of backgrounding that Apple allows.
The iPad will automatically remove apps from RAM as it needs space.
For the most part this works. Sometimes an app starts having problems. Then it is a good idea to remove it from RAM, as described here. That forces it to start clean the next time you open it. Other times the entire OS starts having problems, for whatever reason. Then you need to restart or reset the iPad. Either of these closes all apps.
However, the only non-jailbreak way to remove apps from the multitask bar/list itself is to do so manually, one at a time. Otherwise, they stay there forever, once you've opened them; the most recently opened first.