Cardinal Math

Three-digit subtraction with regrouping · sheet 25 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 970 − 762 208 210 zero minus a number is zero212 smaller from larger or zero minus a number is the number218 borrows, but never pays
2 410 − 396 14 124 borrows, but never pays186 smaller from larger20 zero minus a number is zero26 zero minus a number is the number
3 406 − 368 38 138 borrowing through a zero148 borrows, but never pays162 smaller from larger
4 586 − 489 97 103 smaller from larger107 borrows, but never pays
5 766 − 166 600 no pattern to catch here
6 605 − 355 250 300 zero minus a number is zero350 borrows, but never pays or smaller from larger or zero minus a number is the number
7 979 − 883 96 116 smaller from larger196 borrows, but never pays
8 979 − 371 608 no pattern to catch here
9 907 − 749 158 242 smaller from larger258 borrowing through a zero268 borrows, but never pays
10 922 − 633 289 311 smaller from larger399 borrows, but never pays
11 371 − 312 59 61 smaller from larger69 borrows, but never pays
12 785 − 186 599 601 smaller from larger609 borrows, but never pays
13 930 − 554 376 380 zero minus a number is zero384 zero minus a number is the number424 smaller from larger486 borrows, but never pays
14 601 − 190 411 501 zero minus a number is zero511 borrows, but never pays591 smaller from larger or zero minus a number is the number
15 401 − 228 173 227 smaller from larger273 borrowing through a zero283 borrows, but never pays
16 887 − 496 391 411 smaller from larger491 borrows, but never pays
17 808 − 415 393 403 zero minus a number is zero413 smaller from larger or zero minus a number is the number493 borrows, but never pays
18 386 − 293 93 113 smaller from larger193 borrows, but never pays
19 307 − 208 99 101 smaller from larger109 borrows, but never pays199 borrowing through a zero
20 146 − 137 9 11 smaller from larger19 borrows, but never pays

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 6 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 6 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.