My DS is in first grade at public school. He came home with a worksheet regarding "fact families" which I had never heard of, but by looking at the worksheet seemed to be fairly simple, but I'm a little confused by the grading.
For example:
Fact Family 1, 1, 2
His answers 1+1=2, 2-1=1, 1+1=2, 1-2=-1
He was marked wrong for his last answer and I don't understand why, although I'm guessing he was supposed to repeat 2-1=1, as on subsequent problems that is how he answered and was marked correct.
Anyone familiar with fact families, is there a rule that excludes negative numbers?
Thanks!
For example:
Fact Family 1, 1, 2
His answers 1+1=2, 2-1=1, 1+1=2, 1-2=-1
He was marked wrong for his last answer and I don't understand why, although I'm guessing he was supposed to repeat 2-1=1, as on subsequent problems that is how he answered and was marked correct.
Anyone familiar with fact families, is there a rule that excludes negative numbers?
Thanks!