I came up with this mini abacus to make C because she is very into math right now. She is always asking me, "What is 5+7" or "What is 3+3+3?".
I took a piece of cardboard, cut slots on the sides and added some yarn and beads. Pretty easy.
And now she can do her own math facts :)
I am thinking of writing the number of beads next to each row.