# Easy Permutation-Combination Solved QuestionAptitude Discussion

 Q. A box contains $10$ balls out of which $3$ are red and rest are blue. In how many ways can a random sample of $6$ balls be drawn from the bag so that at the most $2$ red balls are included in the sample and no sample has all the $6$ balls of the same colour?
 ✖ A. $105$ ✔ B. $168$ ✖ C. $189$ ✖ D. $120$

Solution:
Option(B) is correct

Six balls can be selected in the following ways:

One red ball and 5 blue ball

Or
Two red balls and 4 blue balls

Total number of ways:
$= ({^3C_1} × {^7C_5}) + ({^3C_2} × {^7C_4})$

$= 63 + 105$

$= \textbf{168}$