The teacher initially presents a static subtraction. The problem is written on the form and the minuend is formed on the frame. Now we must take away this quantity. Beginning with the units move the beads back to the left. Continue with tens, hundreds and thousands. Read the result and record it.
A second (and all the others following) example is dynamic:
Again the minuend is formed. Beginning with the units we must take away this quantity. Begin counting the units as they are moved back…1,2,3,4,5 we must change one ten to ten units (move one ten back, 10 units forward) and continue…6,7 moving the unit beads back. Subtract tens, hundreds and thousands in the same way. Read and record the result.
CALCULATING THE DIFFERENCE A LITTLE MORE ABSTRACTLY
With a dynamic subtraction again, the child forms the minuend. As before begin by taking away the units. Record the number of units remaining, in the units column. Subtract the tens and so on. The result on the form will correspond to the difference formed on the frame.
Form 1000 on the frame. Subtract one unit. Form 1000 on the frame and subtract 999. Each time three changes are necessary.