Find the volume of a rectangular parallelepiped that is 21 cm long and 3/7 of the length and 30% of the height.

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