You toss 3 coins. What is the probability that you get exactly one head, given that you get at least one tail.

Question

You toss 3 coins.  What is the probability that you get exactly one head, given that you get at least one tail.

tkhunny · Answer

There are only three coins.  Build a tree.

First Flip

H
T

Second Flip

HH
TH
HT
TT

Third Flip

HHH
THH
HTH
TTH
HHT
THT
HTT
TTT

Now count.

anonymous · Answer

I did and created my sample space of 8.  Then I eliminated my HHH combination.  However I see a probability of 3/7 and my text says 2/7.  Am I missing something?

tkhunny · Answer

Let's see...

At least one tails.

Seven Possible Outcomes
THH
HTH
TTH
HHT
THT
HTT
TTT

Exactly 1 heads
Three Possible Outcomes
TTH
THT
HTT

Nope.  You have it.  3/7

anonymous · Answer

Perhaps I have to assume that my first toss is a tails because it is given.  Thank for the help.

tkhunny · Answer

No, don't go questioning a proven, correct response.  Don't do it.  Fight the question if it refuses.