Probabilities/Punnett Square

Question

1. a guy flips a coin 5 times in a row, what is the probability that we get heads each time?
2. a guy flips a coin 10 times in a row, what is the probability that we get heads each time?
3. a guy flips a coin, what is the probability that it lands on heads?
4. a girl flips a coin, what is the probability that it lands on head OR tails?
5. a girl flip two coins, what is the probability that we heads, AND then tails?

Hint: Use the Product Rule and Sum Rule

Please give me an idea on how to do these?

Answer 1

1. 5 time heads is probability of (1/2)^5 = 1/2^5 = 1/32 = 0.03125 = 3.125 % chance
2. 10 times heads? (1/2)^10 = 1/1024 = about 9.77 x 10^-4 = 0.000977 = 0.098 % chance 3.125^2 = about 9.8. move the decimal left 4 times to get .00098 = 0.098%
3. probability of heads on one flip is 1/2 or 50% (assuming a fair coin)
4. probability of either heads or tails = 1 = 100% (assuming it doesn't somehow land on its edge neither head or tail)
5. flip a coin twice. probability of heads then tails = 1/2 x 1/2 = 1/4 = 25% chance

(whether it's a girl or guy who flips makes no difference, Unless you somehow think one or the other gender is more inclined to use an unfair coin. Also most coins are slightly unfair. A coin with a head with slightly more mass will land tails slightly more times. None of the above calculations are correct, if you use either a 2 headed or 2 tailed coin.)