Need help with Pascals triangle?

Question

1.can you predict the number of binomial coefficients when n is 100.
2.How many ones are there in the 21st row of Pascals triangle?explain your answer.
3.What is the rule of how the Pascal triangle is constructed...
4what would happen if the second ellement in a row is a prime number.what can you say about other numbers in that row?

if you can answer any of those questions then you are a genius because i cannot understand one thing here.
thanks

Answer 1

http://mathworld.wolfram.com/PascalsTriangle.html may give you some help..;

Answer 2

http://familyguyvolume4.fanspeak.net/?C1925_528245 may give you some help