Gordon Hamilton's second boomerang addition practice

1. 0
+11
1-20
100
0

2. +12
0
+8
+13
+7
0100

3. +13
0
+8
+12
+7
0100

4. +2
0
+8
+3
+7
0
100
+3
0
+8
+2
+7
0

5. +2
0
+12
+1
+13
0
100
+1
0
+12
+2
+13
0

6. +13
0
+12
+14
+15
0
100
+14
0
+12
+13
+15
0

7. +5
+8
+7
+10
0
61 99

8. +11
+12
+25
+7
0
Numbers
Patterns

9. 0