**And now with coins ... **

Why do biology teachers like to talk about flipping coins so much? Sorry, no punchline here -- the reason is that flipping a coin is alot like meiosis.

What I mean is, when the cell divides to make sperm or eggs, the genetic material also divides. The original cell had 2 copies of each gene (in other words, 2 alleles), but the gamete only gets one. Basically, **the original cell could have "flipped a coin" to determine which copy the gamete ended up with.** And since this happens in both the mother and the father, its like two coins being flipped and the results tallied.

So with that in mind...

### If you flip two coins, what are the chances that both will come up heads?

(To make this problem interactive, turn on javascript!)

- I need a hint ... : P(coin1=heads AND coin2=heads)
- ...another hint ... : This is an AND question, so...

#### I think I have the answer: 1/4

### If you flip two coins, what are the chances that you will get one heads and one tails?

(To make this problem interactive, turn on javascript!)

- I need a hint ... : Be careful!! There are 2 ways this could happen --

first heads then tails, or first tails then heads - ...another hint ... :P((heads AND tails) OR (tails AND heads))
- ...another hint ... :There are 2 ANDs and 1 OR, so you'll need to multiply twice and add once
- ...one last hint?...: (1/2 * 1/2) + (1/2 * 1/2)

#### I think I have the answer: 1/2

### If you flip two coins, what are the chances that you won't get two tails?

(To make this problem interactive, turn on javascript!)

- I need a hint ... : Again, this could happen two ways
- ...another hint ... : tails and tails, or one head and one tail
- ...another hint ... : P(TT) = 1/4 and P(TH or HT)=1/2 (both from the problems above!)

#### I think I have the answer: 3/4

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