Question

The number of noncongruent rectangles that can be formed an a chess board is

• A. $28$
• B. $36$
• C. $64$
• D. $224$

Answer 1

Answer: (B)

$36$

Since

${}^8{C}_2$ is number of ways to select a,b such that a is not equal to b and has other conditions and $8$ is number of ways to select a,b such that $a=b$

So, no. of ways ${=}^8{C}_2+8=28+8=36$