One. Solution: Suppose a box of tea leaves contains a layer of tea barrel. The formed box is a cuboid.
Judging from the title: the bottom of a cuboid is 0.5 meters long, 0.2 meters wide and 0.2 meters high. What is sought here is the surface area of the box. )
Then the surface area is
0.5x0.2x4+0.2x0.2x2=2 (square meters).
After inspection, this is the smallest surface area.
Two. Solution: the weight of black tea is 400x( 1+25%)=500 (ton); The weight of green tea is 500x( 1-25%)=375 (tons).
Three. If the diameter of that flower bed is really ten centimeters, no flowers can be planted, because the perimeter of the flower bed is only 0.1x π = 0.1π (m);
If the diameter of that flower bed is really ten centimeters, you can plant grass 0.05x0.05xπ=0.0025π (square meter).
This is all my answer.
Attachment: I am a sophomore.