Because the two opposite faces are equal in area, count the back two faces first, then the front and back, and finally the left and right faces. Let the length, width and height of a cuboid be a, b and c respectively, then its surface area is S = (ab+bc+ca)×2, which is also equal to 2ab+2bc+2ca, 2(ab+bc+ca).
Introduction to common sense of basic formula:
Mathematical geometry formula of primary school
Circumference:
The circumference of a rectangle = (length+width) × 2 = 2 (a+b) = (a+b) × 2.
The circumference of a square = side length ×4 = 4a.
Circumference = pi× diameter = π d = pi× radius× ×2 = 2πr r r.
Region:
Area of rectangle = length× width S = ab.
Area of a square = side length × side length S = a? .
Area of triangle = base × height ÷2 S=ah÷2.
Area of parallelogram = base × height S=ah.
Trapezoidal area = (upper bottom+lower bottom) × height ÷2 S=(a+b)h÷2.
Baidu encyclopedia-calculation formula