MCQ
If two squares are chosen at random on a chess board, the probability that they have a side common is
  • A
    $\frac{2}{7}$
  • B
    $\frac{1}{18}$
  • C
    $\frac{1}{9}$
  • D
    $\frac{4}{9}$

Answer

(b) $\frac{1}{18}$
Explanation: Total number of squares $=64$.
Two squares can be selected in ${ }^{64} C_2$ ways.
In each column, there are 7 pairs of adjacent squares where each pair share 1 side in common.
Total such pairs $=8 \times 7=56$.
In each row, there are 7 pairs of adjacent squares where each pair share 1 side in common.
Total such pairs $=8 \times 7=56$.
Therefore, favourable cases $=56+56=112$.
Required probability $=\frac{112}{{ }^{64} C_2}=\frac{112}{2018}=\frac{1}{18}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free