① Arrange the numbers of 10 into two columns:

0 5

1 6

2 7

3 8

4 9

Because it's a cycle, you have to work in pairs:

3 8

×

4 9

We can get: 3+9 = 4+8 >; 0+7= 1+6=2+5

②:

Think in the same way:

Arrange the number 10 in two columns:

0 5

1 6

2 7

3 8

4 9

Right minus left: 9-4=8-3=7-2=6- 1=5-0=→↓

↑←←←←←←←←←←

You mean this?