Answer key

The answer, and what a wrong answer means.

#	Problem	Answer	If they wrote…
1	5 + 5	10	no pattern to catch here
2	3 + 3	6	no pattern to catch here
3	9 + 9	18	19 rounding to add, then forgetting to adjust
4	7 + 4	11	no pattern to catch here
5	4 + 3	7	no pattern to catch here
6	7 + 7	14	no pattern to catch here
7	8 + 5	13	15 rounding to add, then forgetting to adjust
8	8 + 8	16	18 rounding to add, then forgetting to adjust
9	3 + 9	12	13 rounding to add, then forgetting to adjust
10	7 + 5	12	no pattern to catch here
11	7 + 1	8	no pattern to catch here
12	9 + 1	10	no pattern to catch here
13	5 + 6	11	no pattern to catch here
14	2 + 1	3	no pattern to catch here
15	4 + 9	13	14 rounding to add, then forgetting to adjust
16	5 + 4	9	no pattern to catch here
17	7 + 4	11	no pattern to catch here
18	9 + 8	17	18 rounding to add, then forgetting to adjust
19	7 + 3	10	no pattern to catch here
20	9 + 9	18	no pattern to catch here

Reading the wrong answers

One wrong answer is a slip. The same pattern on three or more problems is a rule your child is following, and it has a name and a fix. Problems marked "no pattern to catch" are the plain ones; a child who gets only those right is telling you something too.

Reading the wrong answers

Rounding to add, then forgetting to adjust 6 of 20 problems