Question 578753
yes, you have to sum a few terms of the expansion (it shouldn't take "ages")


the expansion is ___ (Pb + Pn)^45 ___ (.22 + .78)^45


1. 43 (or less) are not black
___ subtracting the last 3 terms from one ___  1 - {[(.78)^45] + 45[.22 (.78)^44] + 990[(.22)^2 (.78)^43]}


2.  45C6 [(.22)^6 (.78)^39] = .0572 (approx)


3.  sum those four terms


4.  see #1 ___ 42 (or more) are not black


5.  see #3 ___ 4 (or less) are black