The original surface area was 340 square centimeters. After cutting into two pieces, the extra area is actually the area of the cutting surface. There are three kinds of cutting surfaces, namely 40 50 80 square centimeters. If you want the biggest one, choose 80 square centimeters, and the maximum value is 80*2+340=500 square centimeters.

2

To make a big column is to connect the upper and lower bottom surfaces, so that the total area of the two columns is 100- 15*2=70 square centimeters if the two bottom surfaces are deducted.

three

The increased surface area is the increased lateral area, that is, the perimeter of the bottom * the increased height.

Then the perimeter of the bottom is 25. 12cm and the radius is 4cm, so the added volume is 3. 14 * 4 * 2 =.

100.48cm3

four

There are only two kinds of shells.

One is 60 cm high and the other is 40 cm high. The former has a bottom circumference of 40, which can be calculated as a volume of 7643 cubic centimeters, while the latter has a bottom circumference of 60, with a volume of 1 1465 cubic centimeters.

So surrounded by width and height, it looks heavy.

five

The extra 6 square centimeters come from two cross-sectional areas in the radial direction of the fan, each with a cross-sectional area of 3 square centimeters and a radius of 2, so the height is 1.5cm and the volume is 2 * 2 *1.5 * 3.14 =18.84.