Answer:
1/8
Step-by-step explanation:
To calculate the probability you have to name all possible results first. If you mark a result of a single coin flip as H for heads or T for tails all results of 3 flips can be written as:
Ω
=
{
(
H
,
H
,
H
)
,
(
H
,
H
,
T
)
,
(
H
,
T
,
H)
,
(
H
,
T
,
T
)
,
(
T
,
H
,
H
)
,
(
T
,
H
,
T
)
,
(
T
,T
,
H
)
,
(
T
,
T
,
T
)
}
Each triplet contains results on 1st, 2
nd and 3
rd coin. So you can see that in total there are 8 elementary events in Ω.
|
Ω
| = 8
Now we have to define event A of getting tails three times.
The only elementary event which satisfies this condition is (
T
,
T
,
T
) so we can write that:
A = {
(
T,
T
,
T
)
}
|
A
| = 1
Now according to the (classic) definition of probability we can write, that:
P
(
A
) = |
A|/ |
Ω
| = 1
/8
So finally we can write the answer:
The Probability of getting 3 tails in 3 coin flips is 1
/8
.
