The required materials for scheme (2) are: 2π r+2π× r/2+2π× r/3+2π× r/6 = 4π r.

The two schemes need the same amount of materials.

10. 1.22a， 1.037a，0.037a

1 1. 10a+b, (10b+a)+(10a+b) =11(a+b), and this sum is.

12.⑴ 5a+5b，⑵ 1 1(x+y)？ -(x+y).