Consider an urn with 15 red marbles and 5 blue marbles. Let R_i be the event that the iᵗʰ marble is red. For example:
R₁: The first marble is red
R₂: The second marble is red Suppose we...
a) P(R₁) = ¹⁵⁄₂₀
b) P(R₁) = ⅓
c) P(R₁)= ¾
d) P(R₁)= ³⁄₂₀