Q.

A board has 16 squares as shown in the figure:

       
       
       
       

 

Out of these 16 squares, two squares are chosen at random. The probability that they have no side in common is:          [2025]

1 45  
2 35  
3 710  
4 2330  

Ans.

(1)

Total ways for selecting any two squares =C216=120

Total ways for selecting common side squares =3×4Horizontal side+3×4Vertical side=24

So, required probability =124120=96120=45.