Two-digit addition with carrying

What carrying means

In two-digit addition, you add the ones together and the tens together. If the ones add up to 10 or more, that 10 moves over to the tens place as 1. This is called carrying (or regrouping).

In 38 + 47, the ones are 8 + 7 = 15. 15 is 10 and 5, so write 5 in the ones place and carry the 10 to the tens place as a 1. In the tens place, add the carried 1 as well: 1 + 3 + 4 = 8, so the answer is 85.

Why children find it hard

• They are not yet sure that the small carried 1 actually stands for 10.
• They have to do two things at once: split the ones result, then remember the carried number and add it in the tens place.
• The horizontal format often used in apps and worksheets (38 + 47 = ?) does not make the places easy to see. Until your child is comfortable, it is fine to have them rewrite it vertically on paper.

Steps

1. Write the numbers vertically, lining up the places. Ones under ones, tens under tens.
2. Add the ones first. For 38 + 47, that is 8 + 7 = 15.
3. Carry the 10. Of the 15, write 5 in the ones place and write the 10 as a small 1 above the tens.
4. Add the tens, including the carried 1. 1 + 3 + 4 = 8, so the answer is 85.
5. Check by estimating. 38 is about 40 and 47 is about 50, so an answer close to 90 is on the right track.

Common mistakes

• Forgetting the carried 1. For example, 38 + 47 = 75, where only 3 and 4 were added in the tens place. Getting into the habit of writing the carried 1 small above the tens helps.
• Writing the ones total as is. For example, 38 + 47 = 715, where 15 is written right next to the tens total of 7. Have your child say out loud “15 is 10 and 5.”
• Carrying a 1 even when there is nothing to carry. For example, 23 + 45 = 78, adding 1 out of habit (the correct answer is 68). The app unit mixes in problems without carrying, so have your child check first whether the ones add up to 10 or more.

10 practice problems

Same format as this unit in the app (horizontal, sum of 99 or less), and every problem needs carrying. Tap to see each answer.

1. 38 + 47 = ?
   Answer

   85

2. 26 + 19 = ?
   Answer

   45

3. 57 + 35 = ?
   Answer

   92

4. 18 + 18 = ?
   Answer

   36

5. 45 + 29 = ?
   Answer

   74

6. 63 + 28 = ?
   Answer

   91

7. 34 + 49 = ?
   Answer

   83

8. 19 + 58 = ?
   Answer

   77

9. 12 + 69 = ?
   Answer

   81

10. 47 + 46 = ?
    Answer

    93

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 addition”. If addition without carrying is still shaky, you can also choose “Addition up to 99” to mix the two.
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.