The volume of a rectangular parallelepiped is equal to the product of length, height and width, or the product of the area of the base and height. It doesn’t matter. The length is known, and it is equal to 21 cm. The width is 3/7 of the length, that is, it is necessary to find 3/7 of 21. To do this, we multiply 21 by 3/7 21 * 3/7 and get 9 cm is the width. Height is not specified, but it comes from width. Well, that is, the width is 30% of the height. That is, 30% of the height is 9. To find out the entire height, you need to divide 9 by 0.3 and we get a height of 30 cm. Now it remains to multiply the obtained values 21 * 9 * 30 = 5670 cm³.
Answer: The volume is 5670 cm³
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