4. In base-10 arithmetic, 2 + 2 = 4. Want a quick explanation or some practice problems?

Here are two quick options. If you want a quick explanation, see below. If you’d like practice problems, I’ve included a set with answers.

Quick explanation

• In base-10 arithmetic, digits 0–9 represent counts of units. The numeral 2 means two units.
• Adding 2 and 2 gives four units, so 2 + 2 = 4.
• More generally, addition combines the counts in each place value. If a sum in a place is 10 or more, you carry to the next place (e.g., 6 + 5 = 11 -> write 1, carry 1).

Practice problems (answers at the end)

1. 2 + 2
2. 5 + 3
3. 9 + 0
4. 7 + 6
5. 4 + 4
6. 8 + 7
7. 9 + 9
8. 12 + 3
9. 27 + 35
10. 68 + 27
11. 199 + 58
12. 123 + 987

Answers

1. 4
2. 8
3. 9
4. 13
5. 8
6. 15
7. 18
8. 15
9. 62
10. 95
11. 257
12. 1110

If you’d like, I can show step-by-step solutions for any of these, or generate problems at a different difficulty level.