Enable Javascript in your browser and then refresh this page, for a much enhanced experience.
math solution in Creative category for Pearls in the Box by nennogabriel
checkio=lambda p,n:round(0.5*(1-(1-(2*p.count('w'))/len(p))*pow((1-2/len(p)),n-1)),2)
#These "asserts" using only for self-checking and not necessary for auto-testing
if __name__ == '__main__':
assert checkio('bbw', 3) == 0.48, "1st example"
assert checkio('wwb', 3) == 0.52, "2nd example"
assert checkio('www', 3) == 0.56, "3rd example"
assert checkio('bbbb', 1) == 0, "4th example"
assert checkio('wwbb', 4) == 0.5, "5th example"
assert checkio('bwbwbwb', 5) == 0.48, "6th example"
Aug. 10, 2014