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cancelling out

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bmwhype2
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cancelling out [#permalink] cancelling out   21 Apr 2007, 06:12
this is a probability question.

when a diver dives, there is a 20% chance of a perfect score. however, if a perfect score is given out, no one else will get a perfect score thereafter. janet is the third diver. what are her chances of receiving a perfect score?

8/10 x 8/10 x 2/10 = 128/1000, therefore 12.8%

my question is why cant we cancel out or simplify the fractions in this problem to make it 4/5x 4/5 x 1/5?



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Re: cancelling out [#permalink] cancelling out   21 Apr 2007, 07:08
We can indeed: 4/5 * 4/5 *1/5 =16/125 = 128/1000
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Re: cancelling out [#permalink] cancelling out   21 Apr 2007, 07:16
We can indeed: 4/5 * 4/5 *1/5 =16/125 = 128/1000
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techjanson
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Re: cancelling out [#permalink] cancelling out   22 Apr 2007, 12:55
bmwhype2 wrote:
this is a probability question.

when a diver dives, there is a 20% chance of a perfect score. however, if a perfect score is given out, no one else will get a perfect score thereafter. janet is the third diver. what are her chances of receiving a perfect score?

8/10 x 8/10 x 2/10 = 128/1000, therefore 12.8%

my question is why cant we cancel out or simplify the fractions in this problem to make it 4/5x 4/5 x 1/5?


I am not sure if I get you. You get the same answer either way
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Re: cancelling out [#permalink] cancelling out   14 Jun 2008, 13:10
bmwhype2 wrote:
this is a probability question.

when a diver dives, there is a 20% chance of a perfect score. however, if a perfect score is given out, no one else will get a perfect score thereafter. janet is the third diver. what are her chances of receiving a perfect score?

8/10 x 8/10 x 2/10 = 128/1000, therefore 12.8%


can someone tell me why we only do one outcome
Perfect, Not, Not

and not 2 outcomes
Perfect, Not, Not
Not, Not, Not

Shouldn't this be 2 outcomes that you add together?

Thanks,
Ali
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Re: cancelling out [#permalink] cancelling out   14 Jun 2008, 13:15
h
x-ALI-x wrote:
bmwhype2 wrote:
this is a probability question.

when a diver dives, there is a 20% chance of a perfect score. however, if a perfect score is given out, no one else will get a perfect score thereafter. janet is the third diver. what are her chances of receiving a perfect score?

8/10 x 8/10 x 2/10 = 128/1000, therefore 12.8%


can someone tell me why we only do one outcome
Perfect, Not, Not

and not four outcomes
Perfect, Not, Not
Not, Perfect, Not
Not, Not, Perfect
Not, Not, Not

Thanks,
Ali


Ali,

here the only outcome is NOT, NOT , PERFECT (in that order) since once the Perfect happens it can't happen again and it says that Janet is the 3rd diver
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Re: cancelling out [#permalink] cancelling out   17 Jun 2008, 07:06
kevincan wrote:
We can indeed: 4/5 * 4/5 *1/5 =16/125 = 128/1000

yeaaaaaaaa im a dunce.
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Re: cancelling out [#permalink] cancelling out   17 Jun 2008, 08:55
bmwhype2 wrote:
kevincan wrote:
We can indeed: 4/5 * 4/5 *1/5 =16/125 = 128/1000

yeaaaaaaaa im a dunce.


that was well over a year ago :lol:

u been away bmw?



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