# Thread: 2 coins flip

1. ## 2 coins flip

If I flip two coins 100 times, is there a 50/50 probability of getting heads or tails. True or false?

I know that if I flip two coins I will either get HH, TT, HT or TH.

P(H) is 0.75 for each flip with two coins
P(T) is 0.75 for each flip with two coins

But these probabilities are out of the four possible combinations, and I need them to be out of two, i.e. heads or tails:

So, what is the long term probability of getting either a heads or a tails in the long term? Well, I isn't it 0.5 for each? Because if I flip the coins 100 times and count up how many heads I get and how many tails I get, theoritcally, I should get half of them as heads and half as tails.

Does this sound right?

2. Hello,

Flipping two coins are independent events.

So $P(H \cap H)=P(HH)=P(H)P(H)=0.75^2$

Can you continue ? :P

3. Originally Posted by Moo
Hello,

Flipping two coins are independent events.

So $P(H \cap H)=P(HH)=P(H)P(H)=0.75^2$

Can you continue ? :P
Hi

I'm a bit confused.

P(H) on one of the coins is 0.5
P(H) on the other is also 0.5

independent events, multiply the probabilities giving 0.25 chance of getting a head on both.

I think that is what you are saying.

I think the question is about how many heads would I end up with and how many tails would I end up with after 100 flips.

After 100 flips, there should be 50 heads and 50 tails on the one coin and the same on the other right? Giving 100 heads altogether and 100 tails altogether, in other words 50/50. or am I not understandng this right?

4. But you've been given : "P(H) is 0.75 for each flip with two coins"

Well, i'm a bit lost too, sorry >_<

5. Originally Posted by Moo
But you've been given : "P(H) is 0.75 for each flip with two coins"

Well, i'm a bit lost too, sorry >_<
It's OK, thanks for trying!

I get the bit you said, I just don't get the bit I said! Maybe I'm just confusing myself....

6. Originally Posted by Sweeties
I know that if I flip two coins I will either get HH, TT, HT or TH.

P(H) is 0.75 for each flip with two coins
P(T) is 0.75 for each flip with two coins
Oh I get it. They want to get at least ONE head when you flip TWO coins.

$P(\Omega) = HH , TT , HT , TH$

Let $A$ be the event that you get at least one head.

$P(A) = HH , HT , TH$

Same for tails.