Probability

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Hashgaff
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#1
Report Thread starter 2 years ago
#1
Steve has 12 biscuits in a tin. There are 2 digestive, 7 chocolate and 3 ginger biscuits. Steve takes two biscuits at random from the tin. Work out the probability that he chooses two different types of biscuits.
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psymh5
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#2
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#2
First find the probability of each instance of same type of biscuits:

Digestive Digestive: 2/12 * 1/11 = 1/66
Chocolate Chocolate: 7/12 * 6/11 = 7/22
Ginger Ginger: 3/12* 2/11: 1/22

So, to find possibility of picking different types: 1 - (1/66 + 7/22 +1/22) = 41/66
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philogrobized
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#3
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#3
(Original post by Hashgaff)
Steve has 12 biscuits in a tin. There are 2 digestive, 7 chocolate and 3 ginger biscuits. Steve takes two biscuits at random from the tin. Work out the probability that he chooses two different types of biscuits.
so the possibilities are:
digestive then chocolate
chocolate then digestive
digestive then ginger
ginger then digestive
chocolate then ginger
ginger then chocolate

so then just multiply the probabilities of each happening and add them together

ie first two

(2/12 x 7/11) + (7/12 x 2/11)

then continue with the rest of them....
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Raptor Jesus
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#4
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#4
I think it is 19/50 or 0.38. I think I am wrong. most likely. anyway just answering
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Raptor Jesus
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#5
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#5
ah just looked at the other posts. now I see my mistakes. sorry
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