4:Binomial distribution in python

                    Binomial distribution in python

The ratio of boys to girls for babies born in Russia is . If there is  child born per birth, what proportion of Russian families with exactly  children will have at least  boys?

Write a program to compute the answer using the above parameters. Then print your result, rounded to a scale of  decimal places (i.e.,  format).

Sloution:

pc=str(input())

p1=float(pc[:pc.find(' ')])

p2=float(pc[pc.find(' ')+1:])

pf=0.0

#This is the probability of boy

p = p1/(p1+p2)

from math import factorial as f

def comb(n,r):

    return f(n) / f(r) / f(n-r)

#You have to sum the probabilities of 3,4,5 or 6 boys

for i in range(3,7):

    #You were not using the right formula (it's a multiplication, not a sum)

    prob_i = pow(p,i)*pow(1-p,6-i)*comb(6,i)

    pf += prob_i

print("%.3f"%(pf))