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By M660 on Sunday, December 29, 2002 - 02:26 pm: Edit |

I posted this earlier with a huge typo. Please do this question again if you can.

c.)in a stack of six cards, each card is labeled with a different integer 0 through 5. If two cards are selected at random w/o replacement, what is the probability that their sum will be THREE?

typo=i put 2 instead of 3..thanks for the other answers tho.

By anon2121 on Sunday, December 29, 2002 - 02:28 pm: Edit |

There's 6!/(4!*2!) = 15 combinations of two cards that can be selected. The ones that will equal 3 are {0,3) and {1,2}. Therefore, the probability that the sum will be 3 is 2/15.

By 660M on Sunday, December 29, 2002 - 02:32 pm: Edit |

YES!! I knew there was some weird system i wasnt aware of..bare with me, im only in algebra 2 (11th grade)... explain what these exclamation points mean and how you got 6!4! 2!

By 660M on Sunday, December 29, 2002 - 02:33 pm: Edit |

note: i know how to find the !'s on my ti-83, so its not necessary that you go into a long explanation

By Brian on Sunday, December 29, 2002 - 02:58 pm: Edit |

4! = 4 * 3 * 2 * 1

By Sabzevarian (Sabzevarian) on Sunday, December 29, 2002 - 03:16 pm: Edit |

It is factorial notation. It's not that hard, but I'm not sure if or when you cover that in the US curriculum.

By Pat57575 (Pat57575) on Sunday, December 29, 2002 - 03:32 pm: Edit |

660m, if you were wondering how anon got his answer, the number of combinations that are possible is n!/(r![n-r]!) where n is the total number of cards and r is the size of the groups they are being split into.

**note** in combinations order doesn't matter. {0,3} would be considered the same thing as {3,0}.

By 660M! on Sunday, December 29, 2002 - 05:02 pm: Edit |

THANK YOU!!!! See, i wasnt aware of the formula, ok. Im so happy..this is actually making sense.

BTW, my calc has a whole row of buttons under "Probability". ! is one of them, does anyone know what the others do or if they would be useful for the SAT??

By vp on Monday, December 30, 2002 - 03:08 am: Edit |

LOL....... 660M .... the '!' button is for factorial... its like 6!= 6*5*4*3*2*1...same way 5!= 5*4*3*2*1

ok another thing for probability...the formulae generally dont make sense..so just logic it out....dunno if u guys have conditional prb or baeyers formula/method.....so the one thing that always works...remmeber.....is logic

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