Cardinal Math

Three-digit subtraction with regrouping · sheet 9 of 30

Answer key

The answer, and what a wrong answer means.

The sheet
#ProblemAnswerIf they wrote…
1 744 − 228 516 524 smaller from larger526 borrows, but never pays
2 347 − 199 148 252 smaller from larger258 borrows, but never pays
3 804 − 688 116 216 borrowing through a zero226 borrows, but never pays284 smaller from larger
4 607 − 290 317 407 zero minus a number is zero417 borrows, but never pays497 smaller from larger or zero minus a number is the number
5 243 − 124 119 121 smaller from larger129 borrows, but never pays
6 738 − 209 529 531 smaller from larger539 borrows, but never pays
7 550 − 291 259 260 zero minus a number is zero261 zero minus a number is the number341 smaller from larger369 borrows, but never pays
8 260 − 177 83 117 smaller from larger193 borrows, but never pays90 zero minus a number is zero97 zero minus a number is the number
9 249 − 165 84 124 smaller from larger184 borrows, but never pays
10 208 − 194 14 104 zero minus a number is zero114 borrows, but never pays194 smaller from larger or zero minus a number is the number
11 535 − 302 233 no pattern to catch here
12 867 − 534 333 no pattern to catch here
13 818 − 761 57 157 borrows, but never pays or smaller from larger
14 702 − 463 239 339 borrowing through a zero349 borrows, but never pays361 smaller from larger
15 208 − 179 29 129 borrowing through a zero139 borrows, but never pays171 smaller from larger
16 375 − 299 76 124 smaller from larger186 borrows, but never pays
17 225 − 191 34 134 borrows, but never pays174 smaller from larger
18 560 − 176 384 390 zero minus a number is zero396 zero minus a number is the number416 smaller from larger494 borrows, but never pays
19 200 − 107 93 100 zero minus a number is zero103 borrows, but never pays107 smaller from larger or zero minus a number is the number193 borrowing through a zero
20 307 − 157 150 200 zero minus a number is zero250 borrows, but never pays or 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.