Need shortcuts/ help Math 2

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21

<p>so is it ?
n =3
k=2
p= 1/2</p>

22

<p>3C2 (or 3 choose 2) = 3!/(2!1!) = (3x2x1)/(2x1)(1) = 6/2 = 3.</p>

<p>In general, nCr = n!/((n-r)!r!) and nPr = n!/(n-r)!</p>

23

<p>"so is it ?
n =3
k=2
p= 1/2"</p>

<p>Yes.</p>

24

<p>If it's easy enough to write out the possibilities like I did in #15, just do that. Much harder to make a mistake (if your list is correct!)</p>

25

<p>Sophia, why is it divided by (2^# of flips)?</p>

26

<p>there are 2 possibilities (heads, tails)</p>

<p>2^1 ... H or T ... 2
2^2 ... HT TH HH TT ... 4
2^3 HHH HHT HTH THH HTT THT TTH TTT... 8
etc.</p>

27

<p>2^# of flips is the total possible outcomes. Since first flip could be heads or tails, second flip could be heads or tails, and third flip could also be heads or tails there are 8 ways (2^3) that the experiment could occur. Just like any other probability problem you want do divide "favorable outcome" by "all outcomes"</p>

<p>3C2 / 2^3 = 3/8</p>