Question

If Tom flips a fair coin twice, what is the probability that at least one head will occur?

Answer 1

I mean, there are 4 options, and one head. Is it 1/4?

Answer 2

yeah there are 4 possibilities

Answer 3

@zepdrix

Answer 4

I would look at the probability that you get two tails, then subtract that from 1.

Answer 5

Hum. Let me be sure I understand what you are saying: 1-2/4
or 1-1/2?

Answer 6

those are the same thing

Answer 7

I'm sorry, but I'm confused.

Answer 8

wait I could be wrong it has been a while..

Answer 9

My book says answer is 3/4 but I don't understand how.

Answer 10

there is 1/4 chance you get both tales

Answer 11

There are two different ways that you can flip `at least 1 heads`.
You can either flip `1 heads` or `2 heads`, ya?

Answer 12

Or ya if you look at just the tails that might be easier :D

Answer 13

so 1-1/4

Answer 14

Oh this is different than I was thinking +_+
Back to the drawing board..

Answer 15

Oh ya I guess it's simpler than I was about to make it.
You have four possible flips,
HT
TH
TT
HH

3 of those 4 have at least 1 heads.

Answer 16

If Tom flips a fair coin twice, what is the probability that at least one head will occur?

The possible outcomes:
HH
HT
TH
TT

Answer 17

Ok. I see it now. Thanks!

Answer 18

When you're confused, just list all the possible outcomes (when reasonable to do so)

Answer 19

Yea. That did work out. But this is the first one I have had to do that with. Can you show me the math behind it? Because I like to focus on that end.

Answer 20

Cause at first I said 1/2 * 1/2 and got 1/4. but that is wrong

Answer 21

Any other way is longer and more tedious than just either listing all the outcomes, or just using the fact mentioned earlier:

two tails is 1/2*1/2 and is the only way to get NO heads

So if 1/4 is the chance of zero heads, then 3/4 is the chance of at least one head.

Answer 22

Got ya. Thanks so much. You have helped me so much lately.

Answer 23

Welcome.