2-Digit Subtraction with Regrouping (2nd Grade)

What is it?

Regrouping in subtraction (often called borrowing) is for problems where the top number does not have enough ones to take away. Your child trades 1 ten for 10 ones, so there are enough ones, and then subtracts each place. The lesson uses base-ten blocks: a ten rod breaks into 10 small cubes, so the trade is something you can see, not a rule to memorize.

Step by step: 52 − 27

1. 52 is 5 tens and 2 ones. We take away 27: 2 tens and 7 ones.
2. Start with the ones. Can we take 7 from 2? Not enough.
3. Trade 1 ten for 10 ones. Now there are 4 tens and 12 ones.
4. 12 ones take away 7 ones is 5 ones.
5. 4 tens take away 2 tens is 2 tens. So 52 − 27 = 25.

Common mistakes

• Subtracting the smaller digit from the bigger one in each place (7 − 2 = 5, giving 35). Always take the bottom number from the top.
• Trading the ten but forgetting the tens place now has one less: 5 − 2 = 3 tens instead of 4 − 2 = 2 tens.
• Adding 10 to the ones without taking a ten away.

Your turn

The lesson ends with a problem to try. Pause and let your child work it out before you check.

What is 63 − 28?

Answer: 35. 3 ones is not enough to take away 8, so trade a ten: 6 tens become 5 tens, and 3 ones become 13. 13 − 8 = 5 ones, and 5 tens − 2 tens = 3 tens.

Practice at home

Use dimes for tens and pennies for ones. Build the top number only, then take the bottom number away. When there are not enough pennies, trade a dime for 10 pennies first. Then write the same problem on paper so your child can match each trade to the crossed-out digit.