Question

You flip three coins. What is the probability that you get at least two tails, given that you get at least one tail?

Answer 1

um .... what?

Answer 2

3 coins gives the sample space of:

hhh
hht tth
hth tht
thh htt
ttt

or 8 total

Answer 3

sample space is
thh
hth
hht
tth
tht
htt
ttt
since this are the ones with at least one tail. of those 4 have at least 2 tails so answer is 4/7

Answer 4

P(<=2tails) = 4/8

P(<=1 tail) = 7/8 ... maybe

Answer 5

P(AnB) = 4/8; so maybe if i read it right:

4/8
--- = 4/7 ?
7/8

Answer 6

hello my guru. it says "given that you have at least one tail" which is a conditional probability. you already know one of them is tails, so
hhh is out. that is conditional sample space has 7 elements not 8. of the 7 4 have at least two tails, so get 4/7

Answer 7

if you want a formula you can use
\[P(A|B)=\frac{P(A\cap B)}{P(B)}=\frac{\frac{4}{8}}{\frac{7}{8}}\]

Answer 8

thats what I used :)

Answer 9

thank u cuz i have no clue what im doin here

Answer 10

just wasnt sure if i was reading the ? right :)

Answer 11

ah i see. you are right. site is slow slow slow. or else it is my computer