The length of a round steel is 1.2, now it is sawed into two small sections with each section of 0.6 meters long, and the surface area is increased by 12.56 square centimeters
When a cylindrical steel pipe is sawed into two sections, the increase in surface area is actually the two bottom areas. (1.2m = 120cm)
So the area of the bottom of the cylinder: 12.56 △ 2 = 6.28 square centimeter
Cylinder volume = bottom area × height = 6.28 × 120 = 753.6 cm3
A straight cylinder with a height of 5cm, its side view is rectangular, and the length of the rectangle is 12.56cm. What is the volume of the cylinder?
The bottom area of the cylinder: 3.14 × (12.56 △ 3.14 △ 2) 2, = 3.14 × 4, = 12.56 (square centimeter), the volume of the cylinder: 12.56 × 5 = 62.8 (cubic centimeter). Answer: the volume of the cylinder is 62.8 cubic centimeter
Xiao Ming uses a rectangular piece of paper 18.84 cm long and 12.56 cm wide to form a straight column. How many ways can he use? Which cylinder has the largest volume?
18.84 / 3.14 / 2 = 3 (CM); 3.14 × 32 × 12.56, = 3.14 × 113.04, = 354.9456 (cm3); 12.56 / 3.14 / 2 = 2 (CM); 3.14 × 22 × 18.84, = 3.14 × 75.36, = 236.6304 (cm3); a: there are two methods of girth; when 18.84 cm is the circumference of the bottom surface