Question

you toss 3 coins. what is the probability that you get exactly two heads , given that you at least get one head?

Answer 1

wouldnt it be 2/3?

Answer 2

yes it is..i got it after. thank you

Answer 3

your welcome!

Answer 4

why 2/3?

Answer 5

because there is 3 coins and only 2 possibilities?

Answer 6

no

Answer 7

the answer should be 3/7

Answer 8

ohhh

Answer 9

P(2H|at least one head)

=P(2H,at least one head)/P(at least one head)

=P(2H)/[1-P(3 tails)]=(3/8)/(1-1/8)=(3/8)/(7/8)=3/7

Answer 10

too confusing for me

Answer 11

use the definition of conditional probability

\[P(A|B)=\frac{P(A,B)}{P(B)}\]

Answer 12

list out all the possibilities

HHH
HHT
HTH
THH
HTT
THT
TTH
TTT

only these have at least one head (there are 7 of them)

HHH
HHT
HTH
THH
HTT
THT
TTH

of these only 3 of them have 2 heads

Answer 13

ok....too confusing for me, but i kinda get it a little.