Grade 2 (some late grade 1, review in grade 3) · 2.NBT.5, 2.NBT.7
How do I help my 2nd grader with borrowing?
Subtraction with regrouping (borrowing)
- 52 is five tens and two ones. To take away 8 ones, open a ten: four tens, twelve ones. That's borrowing, all of it.
- The crossing-out just records that move. Stuck children aren't stuck on the notation; they are not yet opening a ten.
- So start with blocks, coins, or sticks and dots, and let a ten split. Paper comes after.
- Find your child's wrong answer below and you've found the rule they're using.
The five-minute check
A short run of problems on a phone or tablet, chosen as your child answers. If one of the six patterns is behind their mistakes, the check names it. Nothing to install, nothing stored.
Hand the phone over, or play it here. When it says all done, take it back and tap see what we found.
Start the five-minute checkThe six ways it goes wrong
- Smaller from larger 52 − 38 they write 26 it is 14 Takes the smaller digit from the bigger one in every column, whichever is on top. Never borrows.
- Borrows, but never pays 52 − 38 they write 24 it is 14 Adds ten to the ones but leaves the tens alone. Looks like borrowing; the answer is ten too big.
- Borrowing through a zero 302 − 167 they write 235 it is 135 Turns the 0 into a 9 and gives the ones their ten, but never reduces the column left of the zero.
- Zero minus a number is the number 40 − 27 they write 27 it is 13 When the top digit is 0, writes the bottom digit as that column's answer.
- Zero minus a number is zero 40 − 27 they write 20 it is 13 When the top digit is 0, writes 0 for that column.
- Within twenty, digit by digit 13 − 5 they write 12 it is 8 Treats 13 − 5 as two separate digits: 3 and 5 give 2, the 1 stays. Smaller-from-larger before there were columns.
What the school is probably doing
- Regrouping / decomposing
- The written method, through tens and ones first; the cross-outs record a ten being opened.
- Counting up on a number line
- From 38, jump 2 to 40, then 12 to 52: the difference is 14. No borrowing; it's how adults make change.
- Expanded form
- 52 − 38 as (40 + 12) − (30 + 8): the regrouping done in the open first.
- Base-ten blocks and drawings
- Sticks for tens, dots for ones. If your child draws these on homework, the lesson is working.
Questions parents ask
What grade is this?
Grade 2 in the US (2.NBT.5), three-digit later the same year (2.NBT.7). Some schools start late in grade 1; most children are still settling it in grade 3.
Is regrouping the same as borrowing?
Yes. The word changed because nothing gets given back: a ten is opened, not lent. If borrowing works at your kitchen table, use it.
My child crosses out everything on the page. Is that bad?
Crossing out is the ritual; opening a ten is the idea. Crossing out every column, needed or not, is the ritual without the idea. Back to objects for a few days.
Should I teach it the way I learned?
Sure. The method you learned is still the method. Just build the number with objects first and ask "where did the ten go?" every time.
They can do it with blocks but not on paper.
That's the normal order. The gap closes when the two stay together: do a problem with blocks and write each step as it happens.
How long should we practise?
Five to ten minutes most days beats an hour on Sunday. Three or four problems done slowly with blocks are worth more than a page.
Cardinal Math watches for all of these, every day.
Inside the app the same patterns are caught as your child plays, across the whole of K to grade 5, and explained to you in plain words. One price, no ads, no streaks. Coming to iPhone and iPad.
Tell me when it's out