### An AHA! abacus moment in the life of a preschooler

I've been doing math lessons with my 3-year old using the 100-bead abacus . Usually we do a few problems where she tells me a two-digit number to make, and I tell her a number to make, back and forth. Today she asked me to make 51, and I asked her to make 68. These went smoothly since she's getting pretty good at this now. Then we did a few "more than" problems. I said, "Let's say your sister has 5 cookies and you have one more than her . How many do you have?" This is a new concept to her, so we need to do it slowly and carefully with the abacus: first make her sister's cookies, then let her have the same amount, then give her one more. Then we did a few subtraction problems such as 7 − 4. She moved 7 beads, then "took away", or moved the other way, 4 beads. How many were left? 3 beads. I also showed her the subtraction 50 − 10 = 40. She started working on her own problem, "Let's do 9 − ..." and while she was thinki