AP EAMCET Engineering 18 Sep 2020 Shift 2 Paper

Total number of ways of selecting 3 square =64C3
Total number of ways of selecting 2 square of one colour and other square of different colour
=(2 white, 1 black) or ( 1 white, 2 black)
=32C2⋅32C1+32C1⋅32C2
=2⋅32C2⋅32C1
Required Probability =‌

2.32C2⋅32C1

64C3

=‌

2⋅ 32×31 2×1 ×32

64×63×62 3×2×1

=‌

16

21