Sample Adding Doubles

Add:
1. 1 + 1
Answer : .
2. 2 + 2
Answer : .
3. 3 + 3
Answer : .
4. 4 + 4
Answer : .
5. 6 + 6
Answer : .
6. 8 + 8
Answer : .
7. 5 + 5
Answer : .
8. 9 + 9
Answer : .
9. 7 + 7
Answer : .
10.10 + 10
Answer : .