Fill parent div on drag 'n drop

Fill parent div on drag 'n drop

Hi, i am having a problem with making a div(.drag) take up all the space when dragged and dropped onto another div(#block)   http://codepen.io/benasl/pen/qaJBPd?editors=0110  . And when moved out of that #block i need the .drag div to be the size it was before.

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I found this simple example of drag and drop http://jsfiddle.net/wj4ak/5/ however still do not know how to make a div fill the parent div when dropped.