# In this program, we flip 100 coins, 1000 times, and we
# compute the proportion of these trials in which between
# 40% and 60% land heads. Try changing the number of coins
# and see how this proportion changes. How many coins do you
# need so that in at least 95% of the trials, the proportion
# is between 40% and 60%?

import random

def pctheads(n):
    v = [random.randint(0,1) for _ in range(n)]
    count = 0.
    for i in v:
        if i == 1:
            count += 1
    return count/n

def close(n,trials):
    v = [pctheads(n) for _ in range(trials)]
    count = 0.
    for i in v:
        if i <= .6 and i >= .4:
            count += 1
    return count/trials

print close(100,1000)