Question

Start with 5 fuchsia, 5 lavender, 5 peach and 5 mauve
colored balls. A ball is chosen at random, its color noticed, its returned to the urn and 5
ball of the same color are added. Suppose that the first 4 moves result in a mauve colored
ball being chosen; what is the probability that the fifth ball chosen is either fuchsia,
lavender or peach?

Answer 1

In the beginning we have 5F + 5L + 5P + 5M = 20 balls

If a ball of a colour is chosen, 5 balls of same colour are added. Since four balls of mauve are chosen, we are adding 5 mauve coloured 4 times, that is 20 balls of mauve

Therefore total balls = 5F + 5L + 5P + 25M = 40 balls

Probabiltiy of the next ball being chosen = (No. of the desired colour) / Total balls

chosing either fuchsia,lavender or peach = P(F) + P(L)+ P(P)

= (5 + 5 + 5 ) / 40

Probability =