How to find the surface area of a rectangular parallelepiped if the areas of its faces are already known?

First, remember that a rectangular parallelepiped has only 6 faces, and every two opposite faces are equal to each other.

Therefore, let the area of the first face be S1, the second – S2, and the third – S3. Then the total surface area of the parallelepiped will be equal to:

S p.p. = 2 * (S1 + S2 + S3).

It should also be noted that if the areas are unknown, but the measurement lengths (a, b, c) are known, then the formula for the total surface will be as follows:

S p.p. = 2 * (a * b + a * c + b * c).