Using a normal deck of cards, children remove the picture cards except for the ace. The ace becomes the 1.
The children partner up and split the cards into two piles facing down. They take it in turns to turn the cards over and add the two numbers together. If they get the correct answer, they keep the cards. If they get the wrong answer, they put the cards at the bottom of the pile.
I have adapted this game to play it with tens and hundreds, e.g. 4=40 etc. I also play subtraction card turnover, where they take the smallest number from the largest number and multiplication card turnover. The children love it.