40+1
39+2
38+3
37+4
36+5
35+6
34+7
33+8
32+9
31+10
30+11
29+12
28+13
27+14
26+15
25+16
24+17
23+18
22+19
21+20
20+21
19+22
18+23
17+24
16+25
15+26
14+27
13+28
12+29
11+30
10+31
9+32
8+33
7+34
6+35
5+36
4+37
3+38
2+39
1+40
These are all operations with natural numbers. More complicated operations look like these:
23,5+17,5 = 41
-1+42 = 41
etc...
... equals an even number
Yes, the sum is always rational.
2+n
70
4507 5267 - 500 - 200 - 60 = 4507