There is a rectangle with a length of 5cm and a width of 4cm, which rotates around the straight line of its length and width respectively to get different cylinders, What are their volumes? Whose is the largest? What kind of enlightenment do you get?

There is a rectangle with a length of 5cm and a width of 4cm, which rotates around the straight line of its length and width respectively to get different cylinders, What are their volumes? Whose is the largest? What kind of enlightenment do you get?

① If you rotate around a long circle,
Volume = 5 * π * 4 & # 178; = 80 π,
② If you rotate around the width,
Volume = 4 * π * 5 & # 178; = 100 π,
It's bulky to go around the width
Inspiration: if you want to get a large cylinder, you should rotate the rectangle around its wide line