Seeing the number relationships

On Monday Sayer noticed something while working on her math pages. If 10 plus 10 equaled 20, and 9 is one less than 10, then 10 plus 9 would have an answer that is 1 less than 20, so, 19. She tried (unprompted by me) to explain it to Mark when he got home that evening. She knew what she was trying to say, but had trouble finding the words. She got pretty close, though :)

She's worked that out again and again since then, sometimes taking it one step farther - starting from 10 plus 10 to get 20, and then 10 plus 9 for 19, and then again, saying that then 9 plus 9 must be 18, because it's 1 less than 10 on both sides of the +, so 2 less than 20.

She's doing the same for subtraction problems :)

And today she had her first math problems where she was asked to add three numbers at the same time. She did great :)