Cardinal Math

Three-digit subtraction with regrouping · sheet 26 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 987 − 521 466 no pattern to catch here
2 920 − 667 253 260 zero minus a number is zero267 zero minus a number is the number347 smaller from larger363 borrows, but never pays
3 708 − 699 9 109 borrowing through a zero119 borrows, but never pays191 smaller from larger
4 562 − 239 323 333 borrows, but never pays337 smaller from larger
5 531 − 260 271 331 smaller from larger371 borrows, but never pays
6 873 − 530 343 no pattern to catch here
7 766 − 271 495 515 smaller from larger595 borrows, but never pays
8 481 − 388 93 103 borrows, but never pays107 smaller from larger
9 901 − 253 648 748 borrowing through a zero752 smaller from larger758 borrows, but never pays
10 975 − 757 218 222 smaller from larger228 borrows, but never pays
11 740 − 651 89 111 smaller from larger199 borrows, but never pays90 zero minus a number is zero91 zero minus a number is the number
12 300 − 254 46 100 zero minus a number is zero146 borrowing through a zero154 smaller from larger or zero minus a number is the number156 borrows, but never pays
13 808 − 651 157 207 zero minus a number is zero257 borrows, but never pays or smaller from larger or zero minus a number is the number
14 741 − 245 496 504 smaller from larger506 borrows, but never pays
15 705 − 608 97 103 smaller from larger107 borrows, but never pays197 borrowing through a zero
16 711 − 353 358 408 zero minus a number is zero442 smaller from larger458 zero minus a number is the number468 borrows, but never pays
17 778 − 392 386 426 smaller from larger486 borrows, but never pays
18 756 − 408 348 352 smaller from larger358 borrows, but never pays
19 603 − 322 281 301 zero minus a number is zero321 smaller from larger or zero minus a number is the number381 borrows, but never pays
20 605 − 375 230 300 zero minus a number is zero330 borrows, but never pays370 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.