If every dimension of a two-dimensional figure is multiplied by k, by what quantity is the area multiplied?

For example: Square has dimension a
A = a²  and if every dimension is multiplied by k new dimension would be:
A 1 = k² a² = k² A.
Or the area of rhombus: A = d1 * d 2 / 2
New area is: A 1 = k d 1 * k d 2 / 2 =  k² A
If every dimension of two-dimensional figure is multiplied by k, the area is multiplied by k².

Yes i could be the length of the triangle