TITLE: Probability of 100 coin tosses
QUESTION [5 upvotes]: I was wondering if I could get some help on this problem. 
Suppose that a fair coin is tossed 100 times. Find the probability of observing at least 60 heads. 
Thanks!
Note: on the study guide I did "1-binomcdf(100,0.50,59)" and still got it wrong
Also, this table is included. 
This is what it looks like. It seems I got it right, but my professor does not approve of my methods. Note the crossed out "-1/2" and "OK"

EDIT: Okay, so the answer is 0.0287. 
I got that by... 1-P(X* < 9.5/5)
=1-P(X* < 1.9)
Then look at the table to find 1.9. 
=1-(0.9713)
=0.0287

REPLY [4 votes]: For a solution that you can do off the top of your head, consider that for a sampling process with N draws and probability of success P, the standard deviation of the approximating normal distribution is:
$$\sigma = \sqrt{( N * P * (1-P) )}$$
for $N = 100$ and $P = 0.5, \sigma = 5$
Fortuitously, your question of 60 or more heads corresponds precisely to a z value of $2 * \sigma$ or more, which every stats student should know is about $2.5%$.  For greater precision, look it up on the table.
I can't speak for your professor, but if you were my student I would award 110% credit and the offer of a paid assistantship if you presented a quick, accurate answer that did not rely on the use of electronic computing.