Online Addition Practice

Over the last two weeks we have been practicing various addition and subtraction problem situations. The students are required to solve various problems including when the start is unknown (ex. ?+4=9), when the change is unknown (ex. 5+?=9), or finding the missing sum (ex. 5+4=?). I found a game online, Count Hoot Addition, that presents addition sentences in this format and increases difficulty as the students achieve success.