3) What is the probability of getting "heads" on every throw when flipping a coin seven times?
1 in ?
The probability of a head on the toss of a coin is 1/2.
If we throw it a second time the results are independent of each other so the probability is 1/2 again.
But, the probability of two heads in a row is 1/2 * 1/2 = 1/4 (another way to look at this is that you can get HH, HT, TH, TT and each is equally likely so that there is a 1 in 4 chance of two heads in a row)
Each time the coin is tossed, the number of possible outcomes doubles (ie, 3 tosses, 8 outcomes:- HHH, HHT, HTH, THH, HTT, TTH, THT, TTT), and there is always only 1 way you can get only heads.
So in 7 tosses, you need to work out how many possible outcomes there are if you keep doubling.
HTH,
Andrew
Cheers,
Andrew