The length of a machine part is 5mm, and the drawing is 4cm. The scale of this drawing is calculated

The length of a machine part is 5mm, and the drawing is 4cm. The scale of this drawing is calculated

According to the distance on the graph: actual distance = scale, the scale can be calculated
4cm: 5mm = 40:5 = 8:1
[note] this is an enlarged scale, because the latter term of the scale is 1; the former term of the reduced scale is 1, and the former and latter terms of the equal scale are 1
(the above answers,)

The shadow is 5 square centimeters, one ninth of the area of the big circle and one sixth of the area of the small circle
How many square centimeters is the blank area? Five more points if the answer is right

5÷1/14×13/14=65

The ratio of the area of the shadow part to the area of the blank part of the big circle is 1:6, and the ratio of the area of the blank part of the small circle is 2:5

∵ the ratio of the area of the shadow part to the area of the blank part of the big circle is 1:6, ∵ the area of the shadow part accounts for 1 / (1 + 6) = 1 / 7 of the big circle ∵ the ratio of the area of the shadow part to the area of the blank part of the small circle is 2:5, ∵ then the area of the shadow part accounts for 2 / (2 + 5) = 2 / 7 of the small circle * (2 / 7) = (π R & # 178 / 7) ∵ the surface of the small circle

The area of the shadow part is 3 square centimeters, which is 18 times of the area of the big circle and 15 times of the area of the small circle?

The blank area of large circle is 3 △ 18-3 = 24-3 = 21 (square centimeter) and that of small circle is 3 △ 15-3 = 15-3 = 12 (square centimeter). The blank area is 21 + 12 = 33 (square centimeter). A: the blank area is 33 square centimeter