Posted by Anonymous on Sunday, February 27, 2011 at 2:11pm.
an unbiased coin is tossed 3 times. find the probability that the coin lands heads exactly once.

math  PsyDAG, Monday, February 28, 2011 at 11:06am
n = # of things to choose from and r = # that you choose.
5! = 5 factorial = 5*4*3*2*1 = 120
nCr = n!/r!(nr)!