Oysi
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| Joined: 06 Jul 2009 |
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| 27 Sep 2011 08:33 AM |
5! = 5*4*3*2*1 4! = 4*3*2*1 100! = 100*99*98*97... |
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LocalChum
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| Joined: 04 Mar 2011 |
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HotThoth
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| Joined: 24 Aug 2010 |
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| 27 Sep 2011 12:35 PM |
An easy way to think about this is that for each fruit, you have two possibilities: either you take it, or you don't. So the total number of possibilities would be 2*2*2*2 = 2^4 different combinations. However, since the problem tells you you have to take at least one fruit, that means you can't leave all of the fruits behind, so the answer you're looking for is 2^4 - 1, or 15. With 100 fruits it'd be 2^100 - 1, or (A REALLY BIG NUMBER).
For a lot of probability problems, I like to use strings, because I find it easier to think about. So for this one, I would line up all the fruits in a row: _ _ _ _, and fill each spot with either a T or an L (whether I take it or leave it). We're not allowed to have LLLL, but all the other possibilities are ok.
Generally, though, when asked this in math classes in the past, the solution recommended was (since there are only 4 fruits) just to count them all :(. As long as you're careful, that's fine [I'd still use the string way, so then I could list them alphabetically and make sure none were missed XD].
And 4! would be the number of ways you could take the fruits if you cared about ordering (if taking the strawberry before the watermelon was different from taking the watermelon before the strawberry). The idea of using a series was not incorrect, but since ordering doesn't matter, you'd want (4 choose 1) + (4 choose 2) + (4 choose 3) + (4 choose 4). This should also work out to 15 :). [Check out binomial coefficients if you've never seen this notation before]. |
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| 27 Sep 2011 12:42 PM |
I thought the question was "How many ways can you arrange four things?" Should probably read things twice before posting. |
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Oysi
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| Joined: 06 Jul 2009 |
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Oysi
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| Joined: 06 Jul 2009 |
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HotThoth
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| Joined: 24 Aug 2010 |
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| 27 Sep 2011 01:22 PM |
Yes-- since you replaced the king (and reshuffled I'm assuming), the events are completely independent from one another. When you have two completely independent events, probability-wise, "AND" is the same as multiplication.
So Prob-of-first-king AND Prob-of-second-king is 1/13 * 1/13. It's a little trickier if you DON'T replace the king and reshuffle, though. |
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Oysi
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epic990
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| Joined: 31 Aug 2010 |
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| 27 Sep 2011 01:51 PM |
| Hotthoth seems a very helpful mod. |
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| 27 Sep 2011 03:24 PM |
| How come mods don't do MY math homework... |
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blocco
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| Joined: 14 Aug 2008 |
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| 27 Sep 2011 03:36 PM |
HotThoth ish an admin
he's better than Sorcus
because he trolls and helps
and he trolls sorcus
so there's +1 right thar |
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myrco1001
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| Joined: 17 Sep 2010 |
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| 27 Sep 2011 03:37 PM |
'so there's +1 right thar' *so there's +9001 right thar
-♂ MYRCO♂- Scripter, music obbsesed, atheist and dutch. What else? |
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Legend26
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| Joined: 08 Sep 2008 |
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| 27 Sep 2011 03:52 PM |
"4/52 * 3/51"
Yea, I think that's right. |
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blocco
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| 27 Sep 2011 03:53 PM |
^
correct because if you take the king out, the numerator and denominator both decrease
gud job Oysi |
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| 27 Sep 2011 05:09 PM |
| Stop making the Mods do your Homework. :-/ |
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ninga95
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| Joined: 16 Jul 2008 |
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| 27 Sep 2011 05:17 PM |
| When I learned probability in math class I was the best at in my class! I just don't practice it so I forgot lol |
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Oysi
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nate890
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| Joined: 22 Nov 2008 |
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| 27 Sep 2011 05:49 PM |
"When I learned probability in math class I was the best at in my class! I just don't practice it so I forgot lol"
:o so was I, hax
<'+1 Post. Ujelly?'> |
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Spectrumw
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| Joined: 04 Aug 2009 |
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| 27 Sep 2011 05:49 PM |
"I just don't practice it so I forgot lol"
I know that feel bro. Vacations == Brain killer. |
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nate890
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| Joined: 22 Nov 2008 |
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| 27 Sep 2011 05:56 PM |
"I know that feel bro. Vacations == Brain killer."
Summer = brain killer
<'+1 Post. Ujelly?'> |
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iamogggg
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| Joined: 09 Sep 2008 |
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| 27 Sep 2011 07:47 PM |
| Today I discovered 27 different ways to kill someone with a logarithm. |
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blocco
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| Joined: 14 Aug 2008 |
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