A box contains 7 red balls. 5 white balls and 3 green balls. In how many ways can we select 3 balls such that-
a. They are all red?
b. They are all white?
c. They are all green?
d. They are different colors?
e. 2 are red and 1 is white?
f. Exactly 2 are white?
g. Exactly 1 is green
h. None is green?

Question

A box contains 7 red balls. 5 white balls and 3 green balls. In how many ways can we select 3 balls such that-
a. They are all red?
b. They are all white?
c. They are all green?
d. They are different colors?
e. 2 are red and 1 is white?
f. Exactly 2 are white?
g. Exactly 1 is green
h. None is green?

sirm3d · Answer

(a) choose 3 red balls among 7. that's combination $\binom{7}{3}$

anonymous · Answer

that is the final answer?

anonymous · Answer

$$\left(\begin{matrix}n \ k\end{matrix}\right)=\frac{n!}{k!(n-k)!}$$