1、

The idea of solving the problem

Calculate how much each supermarket needs, and then decide which one to buy, which is not the cheapest. You should buy 49 books in Lianhua supermarket first, and then buy 4 books in Wenfeng supermarket. This is the best plan.

Problem solving process:

It takes 5× 2 = 10 (yuan) to buy 7 books and 10× 7 = 70 (yuan) to buy 49 books in Hualian Supermarket.

It takes 2× 75 %× 4 = 6 (yuan) to buy 4 books in Wenfeng Supermarket;

A * * * needs 70+6 = 76 (yuan).

2、

Side area with 4 columns: (bottom area does not need painting)

4× 2 π RH = 4× 2× 3.14×1/2× 6 = 75.36 square meters.

Need paint:

75.36× 0.5 = 37.68kg.