Question 610796
We could use a binomcdf but this is very easy to do by hand.


P(4 heads) is simply (1/2)^4 = 1/16.


P(3 heads) is (4C3)(1/2)^4 = 1/4.


Therefore P(3 or more heads) is equal to 1/4 + 1/16, or 5/16.