A diameter of 20 cm, 2 meters long log, according to the volume of the cuboid square wood is how many cubic decimeters

A diameter of 20 cm, 2 meters long log, according to the volume of the cuboid square wood is how many cubic decimeters

The best way is to cut the bottom of the circle into a square, which saves the most materials. In this way, the diameter is the diagonal length of the square;
The diagonal lines of the square are perpendicular to each other, so the square area = 1 / 2 diagonal square
Cuboid volume = square bottom * length = 1 / 2 * 20cm * 20cm * 200cm = 40000 cubic cm = 40 cubic decimeter

When a 2-meter-long log is cut into two sections, its surface area will increase by 40 cubic decimeters. What is the original volume of the log
square meter

40 square decimeter = 0.4 square meter, 0.4 △ 2 = 0.2 is the area of a surface, so 0.2 × 2 = 0.4 cubic meter

A cylindrical wood is 2 meters long. After it is cut into four equal sections, its surface area increases by 18.84 square centimeters?

After cutting it into four equal sections, six additional cross-sectional areas, that is, the area of wood bottom, 18.84/6 = 3.14 square centimeters
2m = 200cm
Volume = 200 * 3.14 = 628 CC