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I did some sums and here are some doubles I made.

20 + 20 = 40

40 + 40 = 80

80 + 80 = 160

160 + 160 = 320

320 + 320 = 640

640 + 640 = 1280

1280 + 1280 = 2560

2560 + 2560 = 5120

5120 + 5120 = 10240

Here are some easier doubles I did. I used the easier doubles to work out the harder ones.
I kn0w 40 +40 = 80 because 4+4=8, so 4 tens + 4 tens = 8 tens and 8 tens is 80.

1 + 1 = 2

2 + 2 = 4

3 + 3 = 6

4 + 4 = 8

5 + 5 = 10

6 + 6 = 12

7 + 7 = 14

8 + 8 = 16

9 + 9 = 18

10 + 10 = 20

11 + 11 = 22

12 + 12 = 24

13 + 13 = 26

14 + 14 = 28

15 + 15 = 30

16 + 16 = 32

17 + 17 = 34

18 + 18 = 36

19 + 19 = 38

20 + 20 = 40

Can you tell me what is going on here?
Can you see a pattern?
What's the change each time?