Cardinal Math

Three-digit subtraction with regrouping · sheet 13 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 998 − 878 120 no pattern to catch here
2 602 − 537 65 135 smaller from larger165 borrowing through a zero175 borrows, but never pays
3 705 − 524 181 201 zero minus a number is zero221 smaller from larger or zero minus a number is the number281 borrows, but never pays
4 682 − 485 197 203 smaller from larger207 borrows, but never pays
5 905 − 164 741 801 zero minus a number is zero841 borrows, but never pays861 smaller from larger or zero minus a number is the number
6 830 − 258 572 580 zero minus a number is zero588 zero minus a number is the number628 smaller from larger682 borrows, but never pays
7 552 − 281 271 331 smaller from larger371 borrows, but never pays
8 731 − 619 112 122 borrows, but never pays128 smaller from larger
9 605 − 297 308 408 borrowing through a zero418 borrows, but never pays492 smaller from larger
10 336 − 307 29 31 smaller from larger39 borrows, but never pays
11 703 − 189 514 614 borrowing through a zero624 borrows, but never pays686 smaller from larger
12 944 − 760 184 224 smaller from larger284 borrows, but never pays
13 404 − 321 83 103 zero minus a number is zero123 smaller from larger or zero minus a number is the number183 borrows, but never pays
14 914 − 802 112 no pattern to catch here
15 780 − 491 289 290 zero minus a number is zero291 zero minus a number is the number311 smaller from larger399 borrows, but never pays
16 326 − 262 64 144 smaller from larger164 borrows, but never pays
17 208 − 199 9 109 borrowing through a zero119 borrows, but never pays191 smaller from larger
18 470 − 197 273 280 zero minus a number is zero287 zero minus a number is the number327 smaller from larger383 borrows, but never pays
19 276 − 267 9 11 smaller from larger19 borrows, but never pays
20 360 − 169 191 200 zero minus a number is zero201 borrows, but never pays209 smaller from larger or zero minus a number is the number

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 18 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 18 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

Zero minus a number is the number 7 of 20 problems

When the top digit is 0, writes the bottom digit as that column's answer.

40 − 27 they write 27 it is 13

Zero minus a number is zero 7 of 20 problems

When the top digit is 0, writes 0 for that column.

40 − 27 they write 20 it is 13

Borrowing through a zero 4 of 20 problems

Turns the 0 into a 9 and gives the ones their ten, but never reduces the column left of the zero.

302 − 167 they write 235 it is 135

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