Page 157 - NUMINO Challenge_D2

Answer 2
Key

Example

Type 9-1 A Section of the Body of Rotation p.78~p.79

1
Type 9-2 Rotated Rectangles with Same Area p.80~p.81

2 1 8 cm 4 cm, 4 cm
8 cm, 2 cm 16 cm , 1 cm
2
2 (Volume) (Area of the Bottom Side) (Height)
Problem solving (Width) (Width) 3.14cm3 Length)

1 If the cylinder is cut into vertical, horizontal, and (Volume of ) 1 1 3.14 16 50.24 cm3
(Volume of ) 2 2 3.14 8 100.48 cm3
diagonal sections, the shapes of the sections are (Volume of ) 4 4 3.14 4 200.96 cm3
as shown below. (Volume of ) 8 8 3.14 2 401.92 cm3
(Volume of ) 16 16 3.14 1 803.84 cm3
Therefore, and cannot be made, even when
the cylinder is cut in different directions. 3 803.84 cm3

Problem solving

1 If a rectangle with a fixed area is rotated around

one of its sides to make a cylinder, the length of
the side which corresponds to the radius of the
cylinder should be the shortest to make the
volume of the cylinder the smallest.

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NUMINO Challenge D2