CK-12 Foundation
Ck 12: Elem Math: Adding and Subtracting Missing Number
[Free Registration/Login may be required to access all resource tools.] The resource is a video showing students how to find a missing number in a multi-step addition and subtraction problem using inverse operations. Adaptive practice...
CK-12 Foundation
Ck 12: Elem Math: Filling in the Missing or Sign Numbers to 1000
[Free Registration/Login may be required to access all resource tools.] The video works through a 3-digit addition problem to determine if the correct operation for the number sentence is addition or subtraction. The video is followed by...