Question

Two squares are chosen at random on a chessboard (see figure). The probability that they have a side in common is :

• A. $\frac{2}{7}$
• B. $\frac{1}{7}$
• C. $\frac{1}{18}$
• D. $\frac{1}{9}$

Answer 1

The correct option is C $\frac{1}{18}$

Total ways $={}^{64}{C}_2$
Favourable ways $=2(8\times 7)=112$
Required probability $=\frac{112}{32\times 63}=\frac{1}{18}$