Cardinal Math

Three-digit subtraction with regrouping · sheet 3 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 303 − 296 7 107 borrowing through a zero117 borrows, but never pays193 smaller from larger
2 544 − 145 399 401 smaller from larger409 borrows, but never pays
3 303 − 209 94 104 borrows, but never pays106 smaller from larger194 borrowing through a zero
4 484 − 393 91 111 smaller from larger191 borrows, but never pays
5 704 − 654 50 100 zero minus a number is zero150 borrows, but never pays or smaller from larger or zero minus a number is the number
6 550 − 278 272 280 zero minus a number is zero288 zero minus a number is the number328 smaller from larger382 borrows, but never pays
7 879 − 385 494 514 smaller from larger594 borrows, but never pays
8 401 − 283 118 218 borrowing through a zero228 borrows, but never pays282 smaller from larger
9 679 − 261 418 no pattern to catch here
10 871 − 798 73 127 smaller from larger183 borrows, but never pays
11 876 − 196 680 720 smaller from larger780 borrows, but never pays
12 787 − 739 48 52 smaller from larger58 borrows, but never pays
13 501 − 151 350 400 zero minus a number is zero450 borrows, but never pays or smaller from larger or zero minus a number is the number
14 404 − 168 236 336 borrowing through a zero346 borrows, but never pays364 smaller from larger
15 555 − 114 441 no pattern to catch here
16 260 − 191 69 131 smaller from larger179 borrows, but never pays70 zero minus a number is zero71 zero minus a number is the number
17 303 − 150 153 203 zero minus a number is zero253 borrows, but never pays or smaller from larger or zero minus a number is the number
18 430 − 406 24 30 zero minus a number is zero34 borrows, but never pays36 smaller from larger or zero minus a number is the number
19 527 − 318 209 211 smaller from larger219 borrows, but never pays
20 442 − 159 283 317 smaller from larger393 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.