There are $10$ points in a plane,out of which $4$ are collinear. How many straight lines can be formed by joining any two of these points?

There are $10$ points in a plane,of which no three points are collinear except $4$. Then,the number of distinct triangles that can be formed by joining any three points of these ten points,such that at least one of the vertices of every triangle formed is from the given $4$ collinear points is

The number of triangles $(T_n)$ that can be formed using the vertices of a polygon with $n$ sides is given by $T_n = \binom{n}{3}$. If $T_{n+1} - T_n = 21$,then what is the value of $n$?

Seven white balls and three black balls are randomly placed in a row. The probability that no two black balls are placed adjacently equals

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

If $a, b, c, d$ are four distinct numbers chosen from the set $\{1, 2, 3, \ldots, 9\}$,then the minimum value of $\frac{a}{b} + \frac{c}{d}$ is