Do you have students who work really fast and then come ask you that ridiculous question, "What do we do when we have finished everything?" Well worry no more, just make it a routine to go to the basket with all of these cards and have them select a card and write their answer on the back using a dry erase card and then turn it back in. If they get it right, they get a prize, if not then the card returns to the basket to be attempted next time.