An abacus has beads that slide on rods. It can be used to count, add, subtract, multiply and more.
• the column on the far right is for ones (1,2,3,...)
• the next column is for tens (10,20,30,...)
• the next column is for 100s (100,200,300,...)
Just like our decimal number system!
Try using the abacus below (in this one the top row is worth 5 of the bottom row):