In and Out/The Pig Pen Game

Today we played a new math game.  It was called "In and Out" or "The Pig Pen Game."
To play you need:
* two ten frames
* a number die
* a +/- die
* 20 counters
To start you roll your number die and place that many counters on the ten frame.  Then you roll the number die and the +/- die together and follow what it says.  For example if you roll 2 and +, you add two counters, but if you roll 2 and -, you must take two counters away.  The object is to fill both ten frames (or pig pens).