The perimeter of an A4 paper is calculated by adding the lengths of all four sides. An A4 paper has dimensions of 21 cm by 29.7 cm, so its perimeter is 2(21 cm) + 2(29.7 cm) = 102.4 cm.
The given scale is not provided, so it is impossible to explain its meaning.
The type of scale shown on the drawing is not provided, so it is impossible to determine whether it is a linear or a non-linear scale.