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

V = abc, where a is the length, b is the length and c is the height of the rectangular parallelepiped.
a = 21 cm.
The width is 3/7 of the length, which means:
b = 21 * 3/7 = 9 (see)
The width is 30% of the height, which means:
c = 9: 30 * 100 = 0.3 * 100 = 30 (see)
V = abc = 21 cm * 9 cm * 30 cm = 5670 cm cubed.
Answer: 5670 cm cubed.