Straight lines are drawn by joining $m$ points on a straight line of $n$ points on another line. Then excluding the given points, the number of point of intersections of the lines drawn is (no tow lines drawn are parallel and no these lines are concurrent). a. $4mn\left(m-1\right)\left(n-1\right)$ b. $\frac{1}{2}mn\left(m-1\right)\left(n-1\right)$ c. $\frac{1}{2}{m}^2{n}^2$ d. $\frac{1}{4}{m}^2{n}^2$

Views: 870 students