If your second grader breezed through subtraction until they hit a problem like 300 − 147, you are not alone. "Borrowing across zeros" is one of the most common sticking points we see in grade 2.
Why zeros are so tricky
With a problem like 52 − 18, your child borrows one ten from the tens place. Easy enough. But in 300 − 147, the tens place has nothing to lend. Your child has to go one more step to the left, to the hundreds, and break a hundred into ten tens before they can borrow a ten. That's two steps of regrouping, and kids often lose track halfway.
Use money to make it real
Kids understand money. Try this at the kitchen table:
- Give your child three $100 bills (play money or paper slips work fine).
- Ask them to pay you $147.
- They'll quickly see they can't do it without "making change." Trade one $100 for ten $10s. Then trade one $10 for ten $1s.
- Now they can hand you $147 and count what's left: $153.
That trading is exactly what regrouping is. Once they've done it with money, show them how the same steps look on paper.
The steps on paper
3 0 0
- 1 4 7- The ones place needs to borrow, but the tens place is 0.
- Go to the hundreds. Change 3 hundreds to 2 hundreds and 10 tens.
- Now borrow one ten. That leaves 9 tens and gives the ones place 10.
- Subtract: 10 − 7 = 3, 9 − 4 = 5, 2 − 1 = 1. The answer is 153.
A helpful shortcut once the idea makes sense: think of 300 as "29 tens and 10 ones." Some children find this faster.
Check the answer by adding
Teach your child to check: 153 + 147 should equal 300. This builds confidence and catches small mistakes before they turn into a bad grade.
When to get help
If your child understands the money version but still struggles on paper after a week or two, the gap is usually place value. They may not yet see that the 3 in 300 means three hundreds. That's very fixable with a few focused sessions.
How Mighty Minds can help
Our grade 2 sessions cover place value to 1,000, adding and subtracting with regrouping, and time and money. We use hands-on tools first and paper second, so the "why" makes sense before the steps.