A cylindrical steel is 2 meters long. If it is sawed into two sections, the surface area will increase by 6.28 square decimeters. The quality of the steel pipe can be calculated (7.8kg per cubic decimeter of steel)

A cylindrical steel is 2 meters long. If it is sawed into two sections, the surface area will increase by 6.28 square decimeters. The quality of the steel pipe can be calculated (7.8kg per cubic decimeter of steel)

The increased surface area is the two bottom areas of the cylinder steel. Then its volume is 3.14 × 20 = 125.6 cubic decimeter, and its mass is 125.6 × 7.8 = 979.68 kg

The bottom radius of a cylinder is 3 decimeters and the height is 8 meters. After sawing it into two sections, the surface area increases______ Square decimeter

3.14 × 32 × 2, = 3.14 × 9 × 2, = 56.52 (square decimeter). A: after sawing it into two sections, the surface area increases by 56.52 square decimeter

A 5-meter-long cylindrical timber is sawed into 4 sections, and the surface area is increased by 60 square decimeters______ Cubic decimeter

5 meters = 50 decimeters, bottom area: 60 △ 6 = 10 (square decimeters), 10 × 50 = 500 (cubic decimeters); answer: the volume of this wood is 500 cubic decimeters. So the answer is: 500