vix.xvi
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#1
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#1
yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks
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DFranklin
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#2
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Values in table should add up to 1.
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mqb2766
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#3
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(Original post by vix.xvi)
yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks
The fifth roll is final. The probabilities should add to 1, by definition.
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vix.xvi
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(Original post by mqb2766)
The fifth roll is final. The probabilities should add to 1, by definition.
(Original post by DFranklin)
Values in table should add up to 1.
ohh ok
so to work out the 5th roll you just do
(3/7)^4 x (4/7) right?
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the bear
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(Original post by vix.xvi)
yeah im a bit confused cuz i got a different value for the 5th roll. i got 324/16807 which is not the same as what the answers say.

Also should i expect all the values in the table to add up to one?

thanks
once you have gone past 4 spins you know that you are on the final spin as the game stops. so to find P ( x = 5 ) you just work out 1 - P ( x < 5 )... in other words add up the previous 4 answers and subtract from 1.
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vix.xvi
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(Original post by the bear)
once you have gone past 4 spins you know that you are on the final spin as the game stops. so to find P ( x = 5 ) you just work out 1 - P ( x < 5 )... in other words add up the previous 4 answers and subtract from 1.
ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)
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mqb2766
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(Original post by vix.xvi)
ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)
There is no assumption of the colour on the fifth throw.
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vix.xvi
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(Original post by mqb2766)
There is no assumption of the colour on the fifth throw.
ahhhh

that makes sense, thank you!!
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DFranklin
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(Original post by the bear)
once you have gone past 4 spins you know that you are on the final spin as the game stops. so to find P ( x = 5 ) you just work out 1 - P ( x < 5 )... in other words add up the previous 4 answers and subtract from 1.
In this case it's probably easier to directly work out P(x > 4) (i.e. P(no G's on previous rolls)).
(Original post by vix.xvi)
ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)
(3/7)^4 x (4/7) is the probability of not rolling a G on the first 4 rolls and then rolling a G on the 5th.
But you're going to stop after the 5th roll regardless of whether you roll a G on the 5th roll. So you just want (3/7)^4.
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the bear
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(Original post by DFranklin)
In this case it's probably easier to directly work out P(x > 4) (i.e. P(no G's on previous rolls)).

(3/7)^4 x (4/7) is the probability of not rolling a G on the first 4 rolls and then rolling a G on the 5th.
But you're going to stop after the 5th roll regardless of whether you roll a G on the 5th roll. So you just want (3/7)^4.
yharapbtur
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vix.xvi
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(Original post by DFranklin)
In this case it's probably easier to directly work out P(x > 4) (i.e. P(no G's on previous rolls)).

(3/7)^4 x (4/7) is the probability of not rolling a G on the first 4 rolls and then rolling a G on the 5th.
But you're going to stop after the 5th roll regardless of whether you roll a G on the 5th roll. So you just want (3/7)^4.
thanks so much!
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the bear
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(Original post by vix.xvi)
ohhh ok

sorry but why is this not the same as the answer you et when you do (3/7)^4 x (4/7)
because the final probability is (3/7)4 * 1
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vix.xvi
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(Original post by the bear)
because the final probability is (3/7)4 * 1
wait why is it multiplied by 1?
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DFranklin
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(Original post by vix.xvi)
wait why is it multiplied by 1?
(3/7)^4 is the probability you get to the 5th
throw. 1 is the probability that once you get to the 5th throw, you finish.

Obviously the "multiply by 1" doesn't actually do anything, but it's in contrast to the previous rounds where there's a 4/7 chance of finishing.
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vix.xvi
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(Original post by DFranklin)
(3/7)^4 is the probability you get to the 5th
throw. 1 is the probability that once you get to the 5th throw, you finish.

Obviously the "multiply by 1" doesn't actually do anything, but it's in contrast to the previous rounds where there's a 4/7 chance of finishing.
Oooh ok thank you!!☺️☺️
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