=220 Number of ways to draw exactly 2 red balls and 1 non-red ball =4C2×8C1=6×8=48 Number of ways to draw exactly 2 green balls and 1 non-green ball =5C2×7C1 =
5!
2!×3!
×
7!
1!6!
=10×7=70 Number of ways to choose 2 white balls from 3. =3C2 Number of ways to draw exactly 2 white balls and 1 non-white ball =3C2×9C1=
3!
2!×1!
×
9!
1!8!
=3×9=27 Total number of ways to draw exactly 2 balls of the same colour =48+70+27=145 ∴ Required probability =
