Urn Without Replacement Probability

Problem

An urn has red red balls and blue blue balls. The probability of drawing k reds in a row without replacement is prod_{j=0}^{k-1} (red - j) / (red + blue - j).

Given red, blue, and k (with k <= red), return the probability.

Hint

Multiply the sequential conditional probabilities.

Test cases

case 1

in: [5,5,2]

expected: 0.2222222222222222

case 2

in: [3,1,2]

expected: 0.5

case 3

in: [10,0,3]

expected: 1

Starter codePython

def urn_without_replacement_probability(red, blue, k):
    # Your code here
    pass

3 test cases · run your code against them in the editor