Two-digit subtraction with borrowing

What borrowing means

Two-digit subtraction also starts with the ones. But in 53 − 28, the top ones digit (3) is smaller than the bottom one (8), so you cannot subtract as is. Taking one 10 from the tens and adding it to the ones is called borrowing (or regrouping).

If you take one ten from the 5 tens in 53, the tens become 4 and the ones become 13. 13 − 8 = 5 and 4 − 2 = 2, so the answer is 25.

Why children find it hard

• Remembering only the rule “take the smaller number from the bigger one,” they easily subtract backwards in the ones place, like 8 − 3.
• They forget to reduce the tens digit by 1 after lending 10.
• When the ones digit is 0, as in 30 − 14, they stop at “How can I take away from 0?”

Steps

1. Write the numbers vertically, lining up the places. If the number being subtracted has one digit, as in 42 − 7, write the 7 under the ones.
2. Compare the ones. If the top digit is smaller than the bottom digit, you need to borrow. In 53 − 28, 3 is smaller than 8.
3. Borrow 10 from the tens. Cross out the 5 in the tens place and write 4, then change the 3 in the ones place to 13.
4. Subtract the ones. 13 − 8 = 5
5. Subtract using the reduced tens. 4 − 2 = 2, so the answer is 25.
6. Check with addition. If 25 + 28 = 53, the answer is right.

Common mistakes

• Subtracting the ones backwards. For example, 53 − 28 = 35: 8 cannot be taken from 3, so 3 is taken from 8 instead. Have your child say “top minus bottom” out loud while solving.
• Not reducing the tens after lending. For example, 71 − 34 = 47: the ones were done correctly as 11 − 4, but the tens digit was left as 7 (the correct answer is 37). Crossing out and writing the reduced number above helps.
• Leaving a 0 in the ones place as is. For example, 30 − 14 = 20, where the ones digit stays 0 (the correct answer is 16). Practice separately that a 0 becomes 10 when you borrow.

10 practice problems

Same format as this unit in the app (horizontal, subtracting from 15 to 94), and every problem needs borrowing. Tap to see each answer.

1. 42 − 7 = ?
   Answer

   35

2. 53 − 28 = ?
   Answer

   25

3. 71 − 34 = ?
   Answer

   37

4. 30 − 14 = ?
   Answer

   16

5. 64 − 9 = ?
   Answer

   55

6. 85 − 47 = ?
   Answer

   38

7. 92 − 58 = ?
   Answer

   34

8. 26 − 18 = ?
   Answer

   8

9. 50 − 23 = ?
   Answer

   27

10. 81 − 63 = ?
    Answer

    18

Practicing this unit in the app

1. Open the Create tab at the bottom of the app. If you have not added your child yet, add them in the Children tab first.
2. Under 📚 Select Level, tap Lv.6 (Ages 8-9), then under 📖 Select Unit choose “2-digit subtraction”. To practice it mixed with addition, also choose “2-digit addition”.
3. Set the number of problems with the − and + buttons on the unit card, or tap ✏️ to type a number. 5 to 10 problems is an easy start.
4. Choose your child under 👶 For whom? and create the problems. Your child can solve them on their own device, or tap Solve on this phone now right after creating to solve on your phone.
5. When your child submits, open the worksheet and tap ✅ Grade Now. The correct answer and your child's answer are shown for each problem.
6. If any answers are wrong, tap ❌ Retry Wrong Answers on the results in your child's screen. The correct answers are shown only after they submit again.
7. Check the accuracy for each unit in the Progress tab. 90% or higher is shown as Good, 70-89% as Average, and below 70% as Weak.