Push all the beads on the 100-bead abacus to one side. Starting with the bottom row, slide the beads to the other side one at a time, counting them as you go. Show your child that there are 10 beads on each row.
Model addition or subtraction using the 100-bead abacus. Demonstrate 2+3 = 5 by sliding three beads across the bottom rod, then sliding two more across, then counting them all. Demonstrate 5-3 = 2 by sliding three back the other way and counting the remainder.
Model counting by 10s by sliding an entire row of beads across and counting it as 10. Then slide a second row across and count it as 20. Continue this way until you have reached 100.
Demonstrate place value to older children on a Chinese abacus. Using the far right column, slide each bead in the bottom section from bottom to top, counting to 5 as you go. Then slide one of the beads above the crossbar to the top, and reset the bottom beads.
Repeat the process on the same crossbar, sliding the second upper bead to the top when you have counted to 5. Point out to your child that you have now counted to 10, and both beads above the crossbar are pressed to the top.
Move to the second column from the right and slide one of the lower beads to the top, and tell your child that this represents the 10 you have just counted. Slide the beads in the right-hand column to the bottom again, and repeat the counting process in that column. Slide a second lower bead to the top in the 10s column. Explain that this represents that you have now counted to 20.
Continue counting like this until you reach 50, then slide one of the upper beads in the 10s column to the top, and return the lower beads to the bottom. Explain to your child that each column represents a place value, just like digits in a numeral.