The Dot Game: Dynamic subtraction (with change)

How is dynamic subtraction done with the Dot Game?

The directress begins the activity by reading through the operation with the child that is written on the dot paper in expanded notation, for example: (8752 - 6435) The directress draws two dots in the green marker in the unit column. She then asks the child to draw five blue dots in the tens column, seven red dots in the hundreds column and, eight green dots in the thousands column.

The directress reminds the child that they need to take five units away. The child realizes that they cannot take five away from two. The directress then reminds him that they can take one ten away from the tens column and draw 10 dots in the units collum, as they are the same. She crosses out a dot in the tens collum and places 10 dots in the units column. The child now notices that five can be subtracted.

The child counts and records the answer in the green marker in the units column. The child is encouraged to continue in the same manner with the same tens, hundreds, and thousands exchanging if need be and counting and recording the answer in the correct column, using the correct colour marker.

Once the operation is complete, the directress reads through the answer with the child and helps him to pack away.