91Ó°ÊÓ

We are given an urn containing 7 white balls and 3 red balls. Three balls are selected. In how many ways can the 3 balls be drawn from the total of 10 balls if 2 balls are white and 1 is red

We know that we have a total of 7 white ball and 3 red balls.The ways to draw 2 white ball and 1 red ball is :

$C(7,2)×C(3,1)=\frac{7!}{2!5!}×\frac{3!}{1!2!}$

$\frac{7×6×5!}{2×1×5!}×\frac{3×2!}{1×2!}=\frac{7×6}{2}×\frac{3}{1}$

$7×3×3=63$ways

We are given an urn containing 7 white balls and 3 red balls. Three balls are selected. In how many ways can the 3 balls be drawn from the total of 10 balls if all 3 balls are white?

We know that we have a total of 7 white ball and 3 red balls.The ways to draw 3 white balls :

$C(7,3)=\frac{7!}{3!}$

$\frac{7×6×5×4!}{4!×3×2×1}=\frac{7×6×5}{3×2×1}$

$7×5=35$ways

We are given an urn containing 7 white balls and 3 red balls. Three balls are selected. In how many ways can the 3 balls be drawn from the total of 10 balls if all 3 balls are red?

We know that we have a total of 7 white ball and 3 red balls.The ways to draw 3 red balls :

$C(3,3)=\frac{3!}{3!×0!}$

$\frac{3!}{3!}=1$way