Answer key

The answer, and what a wrong answer means.

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

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