From a box containing 6 white balls and 4 black balls 4 ball

From a box containing 6 white balls and 4 black balls, 4 ballsare drawn at random. Find the probability that 3 were white, and 1 was balck.

a.) If each ball was returned before the next was drawn.

b.) if the 4 balls were drawn successively without replacement.

Solution

a.) If each ball was returned before the next was drawn.

6/10*6/10*6/10 *4/10 = 54/625 (ans) or 0.0864 (ans)

b.) if the 4 balls were drawn successively without replacement.

6C₃ *4C₁/10C₄ = 0.38095 (ans) or 8/21 (ans)