Cardinal Math

Three-digit subtraction with regrouping · sheet 1 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 611 − 207 404 414 borrows, but never pays416 smaller from larger
2 603 − 539 64 136 smaller from larger164 borrowing through a zero174 borrows, but never pays
3 677 − 436 241 no pattern to catch here
4 503 − 204 299 301 smaller from larger309 borrows, but never pays399 borrowing through a zero
5 987 − 309 678 682 smaller from larger688 borrows, but never pays
6 704 − 181 523 603 zero minus a number is zero623 borrows, but never pays683 smaller from larger or zero minus a number is the number
7 938 − 699 239 349 borrows, but never pays361 smaller from larger
8 268 − 199 69 131 smaller from larger179 borrows, but never pays
9 650 − 481 169 170 zero minus a number is zero171 zero minus a number is the number231 smaller from larger279 borrows, but never pays
10 502 − 144 358 442 smaller from larger458 borrowing through a zero468 borrows, but never pays
11 280 − 194 86 114 smaller from larger196 borrows, but never pays90 zero minus a number is zero94 zero minus a number is the number
12 833 − 343 490 510 smaller from larger590 borrows, but never pays
13 322 − 252 70 130 smaller from larger170 borrows, but never pays
14 946 − 585 361 441 smaller from larger461 borrows, but never pays
15 260 − 186 74 126 smaller from larger184 borrows, but never pays80 zero minus a number is zero86 zero minus a number is the number
16 710 − 306 404 410 zero minus a number is zero414 borrows, but never pays416 smaller from larger or zero minus a number is the number
17 605 − 575 30 100 zero minus a number is zero130 borrows, but never pays170 smaller from larger or zero minus a number is the number
18 658 − 435 223 no pattern to catch here
19 606 − 386 220 300 zero minus a number is zero320 borrows, but never pays380 smaller from larger or zero minus a number is the number
20 401 − 173 228 328 borrowing through a zero338 borrows, but never pays372 smaller from larger

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.