The common-core math standards require that students learn the standard algorithm for multi-digit adding and subtracting—you know, the process in which you line the numbers up vertically to add or ...

When you subtract using large numbers, it's often better to use a written method. Column subtraction is a good written method to take one number away from another. It involves writing the smaller ...

Picture a bridge made of Legos. One side has three support pieces, the other two. How would you stabilize the bridge? Most people would add a piece so that there are three supports on each side, a new ...

When you subtract using large numbers, it's often better to use a written method. Column subtraction is a good written method to take one number away from another. It involves writing the smaller ...