There are $16$ points in a plane out of which $6$ are collinear. How many lines can be drawn by joining these points?

How many necklaces can be formed by selecting $4$ beads from $6$ different colored glass beads and $4$ beads from $5$ different colored metal beads?

Six '$X$'s have to be placed in the squares of the figure such that each row contains at least one '$X$'. In how many different ways can this be done?

The number of rectangles that can be obtained by joining four of $12$ vertices of a $12$-sided regular polygon is:

The number of triangles that can be formed by choosing the vertices from a set of $12$ points,$7$ of which lie on the same straight line,is

If in a regular polygon the number of diagonals is $54$,then the number of sides of this polygon is