Question

You toss 3 coins. What is the probability that you get exactly 3 heads, given that you get at least one head? A tree diagram will help you to answer this question.

Answer 1

@mathmate

Answer 2

You already know that one of the three coins is going to be heads. So, what you're really looking for is the probability that the other two coins are both heads.

What is the probability of flipping two coins and they are both heads?

Answer 3

so... HHT would be one?

Answer 4

Possible let's say HHH and TTT but it does not have one head. Understand ?

Answer 5

i understand why TTT isnt but HHH does

Answer 6

@music101 It's simpler than you're making it. The first coin is irrelevant because we know it's heads. So make this into a new problem:

If we flip two coins, what is the probability that both coins are heads?

Answer 7

2/2 ?

Answer 8

or 1/4

Answer 9

Right, 1/4, since each coin has a 1/2 probability of being heads and there are two coins, so:
(1/2)(1/2)=1/4

Answer 10

Me personal I will say 3/7 . Because their are 7 situations with probably one head and 3 two.

Answer 11

so then..

Answer 12

so theyre asking u to find the probability that you actually get TWO heads??

Answer 13

@vinnv226

Answer 14

@music101 Right. You're flipping three coins. The first coin is definitely heads, so we can put it aside and look at the two remaining coins. There is a 1/4 probability of these other coins both being heads.

Answer 15

oh cuz its 1/2* 1/2?

Answer 16

so the answer is 1/4?

Answer 17

Yes, I believe thats correct. You could check it using another method, like tree diagrams

Answer 18

I have no clue how to do that that's why I asked this in the first place :(

Answer 19

how would u do that??

Answer 20

I gonna submit 1/4

Answer 21

There are eight outcomes when you throw a coin 3 times, one of which is TTT, and another is HHH.
"Given that you have at least one head" means you would ignore the case TTT, that leaves you with 7 outcomes.
So P(HHH)=1/7.

Answer 22

:( I already submitted 1/4 :( :( this sucks!

Answer 23

We've all given a lot of different answers here, but I don't think any of us have drawn the tree diagram yet...maybe we could agree on an answer if we do

Answer 24

ok.. but right now I need help w/ the other question