Consider the 20 points of a 4×5 grid. You randomly choose two points from the 20 points. What is the probability that the two points belong to a horizontal or vertical line?

Guest Feb 28, 2021

#1**0 **

if the two points can be the same point, then the answer is $\boxed{\frac{(4+4)\cdot20}{20\cdot20}=\frac25}$

if the two points are different, then the answer is $\boxed{\frac{(4+3)\cdot20}{20\cdot19}=\frac7{19}}$

SparklingWater2 Feb 28, 2021