Fitting Rectangles

To prepare for Equinox the team is making decorations, one of these decorations is a square, but they only have rectangular papers of ratio 1:n to make the square. Assume that the actual size of the rectangle can be anything as long as the sides are in ratio 1:$n$. You want to use exactly $k$ of these rectangles to make the square in such a way that there are _*no gaps or overlaps*_ Given n and k,