Cardinal Math

Two-digit subtraction with regrouping · sheet 24 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 60 − 53 7 13 smaller from larger17 borrows, but never pays
2 78 − 69 9 11 smaller from larger19 borrows, but never pays
3 76 − 47 29 31 smaller from larger39 borrows, but never pays
4 90 − 81 9 11 smaller from larger19 borrows, but never pays
5 91 − 84 7 13 smaller from larger17 borrows, but never pays
6 58 − 29 29 31 smaller from larger39 borrows, but never pays
7 92 − 23 69 71 smaller from larger79 borrows, but never pays
8 80 − 64 16 24 smaller from larger26 borrows, but never pays
9 90 − 17 73 83 borrows, but never pays87 smaller from larger
10 77 − 29 48 52 smaller from larger58 borrows, but never pays
11 70 − 69 1 11 borrows, but never pays19 smaller from larger
12 35 − 31 4 no pattern to catch here
13 73 − 45 28 32 smaller from larger38 borrows, but never pays
14 85 − 79 6 14 smaller from larger16 borrows, but never pays
15 97 − 59 38 42 smaller from larger48 borrows, but never pays
16 87 − 39 48 52 smaller from larger58 borrows, but never pays
17 38 − 18 20 no pattern to catch here
18 89 − 88 1 no pattern to catch here
19 89 − 27 62 no pattern to catch here
20 79 − 69 10 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.