Square with sides measuring 12 in. what is the perimeter and area?

48 is the perimeter, all sides in a square are equal, you take 12 * 4 which gives you 48.

For the area, you take two sides, length and width, and you multiply them, 12 * 12, this gives you 144.

Well a square has 2 dimensions (used for area) and 4 sides (used for perimeter).  Perimeter is the measure of the total outside length of a shape, and since there are 4 sides on a square and each side of the square is 12 inches long, the perimeter can be found by multiplying the length of each side by the number of sides (12 x 4 = 48).
P = 48 inches
Area is the measure of the square units taken up by the shapes interior, so you multiply the lengths of the two dimensions in a square by each other to find the area (12 x 12 =144).
A = 144 inches^2