Cardinal Math

Two-digit subtraction with regrouping · sheet 6 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 69 − 39 30 no pattern to catch here
2 92 − 88 4 14 borrows, but never pays16 smaller from larger
3 82 − 64 18 22 smaller from larger28 borrows, but never pays
4 99 − 84 15 no pattern to catch here
5 65 − 57 8 12 smaller from larger18 borrows, but never pays
6 99 − 55 44 no pattern to catch here
7 51 − 39 12 22 borrows, but never pays28 smaller from larger
8 90 − 84 6 14 smaller from larger16 borrows, but never pays
9 70 − 61 9 11 smaller from larger19 borrows, but never pays
10 80 − 16 64 74 borrows, but never pays76 smaller from larger
11 83 − 67 16 24 smaller from larger26 borrows, but never pays
12 80 − 14 66 74 smaller from larger76 borrows, but never pays
13 95 − 77 18 22 smaller from larger28 borrows, but never pays
14 96 − 88 8 12 smaller from larger18 borrows, but never pays
15 40 − 19 21 31 borrows, but never pays39 smaller from larger
16 93 − 91 2 no pattern to catch here
17 92 − 58 34 44 borrows, but never pays46 smaller from larger
18 58 − 29 29 31 smaller from larger39 borrows, but never pays
19 96 − 18 78 82 smaller from larger88 borrows, but never pays
20 12 − 11 1 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 in the guide. Problems marked "no pattern to catch" are the plain ones; a child who gets only those right is telling you something too.

Borrows, but never pays 15 of 20 problems

Adds ten to the ones but leaves the tens alone. Looks like borrowing; the answer is ten too big.

52 − 38 they write 24 it is 14

Smaller from larger 15 of 20 problems

Takes the smaller digit from the bigger one in every column, whichever is on top. Never borrows.

52 − 38 they write 26 it is 14

Not sure which? The five-minute check picks the problems that tell the patterns apart and names the one it sees.