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GCSE Maths Probability Question
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abbie1259
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#1
Hello, I'm really struggling with probability questions and I'd be very grateful if somebody could explain to me how to do the following question:
'Carolyn has 20 biscuits in a tin.
She has
12 plain biscuits
5 chocolate biscuits
3 ginger biscuits.
Carolyn takes at random two biscuits from the tin.
Work out the probability that the two biscuits were not the same type.'
Thank you!
'Carolyn has 20 biscuits in a tin.
She has
12 plain biscuits
5 chocolate biscuits
3 ginger biscuits.
Carolyn takes at random two biscuits from the tin.
Work out the probability that the two biscuits were not the same type.'
Thank you!
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Pinixy5
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#2
Hey,
The probability would be:
The total number of biscuits = 20
(plain, plain) = (12/20)(11/19) = 132/380
(chocolate,chocolate) = (5/20)(4/19) = 20/380
(ginger,ginger) = (3/20)(2/19) = 6/380
Probability (they both are of the same type) = 132/380+ 20/380 + 6/380 = 158/380 = 79/190
Probability (they were not the same type.) = 1- 79/190 = 111/190
I hope this helps. :-)
The probability would be:
The total number of biscuits = 20
(plain, plain) = (12/20)(11/19) = 132/380
(chocolate,chocolate) = (5/20)(4/19) = 20/380
(ginger,ginger) = (3/20)(2/19) = 6/380
Probability (they both are of the same type) = 132/380+ 20/380 + 6/380 = 158/380 = 79/190
Probability (they were not the same type.) = 1- 79/190 = 111/190
I hope this helps. :-)
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abbie1259
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#3
(Original post by Hammarobi)
Hey, i can quickly, tell you what it is, and what to revise, i'm sure someone else can tell you step by step (I would but I've gotta go, Sorry)
It's a probability tree diagram, this uses 3 lines, and has two of the diagrams as she takes 2 Biscuits.
The tree diagram is a, how i like to remember them, a webbed foot like drawing.
(I'll finish this off later if someone else doesn't come)
Hey, i can quickly, tell you what it is, and what to revise, i'm sure someone else can tell you step by step (I would but I've gotta go, Sorry)
It's a probability tree diagram, this uses 3 lines, and has two of the diagrams as she takes 2 Biscuits.
The tree diagram is a, how i like to remember them, a webbed foot like drawing.
(I'll finish this off later if someone else doesn't come)
(Original post by Pinixy5)
Hey,
The probability would be:
The total number of biscuits = 20
(plain, plain) = (12/20)(11/19) = 132/380
(chocolate,chocolate) = (5/20)(4/19) = 20/380
(ginger,ginger) = (3/20)(2/19) = 6/380
Probability (they both are of the same type) = 132/380+ 20/380 + 6/380 = 158/380 = 79/190
Probability (they were not the same type.) = 1- 79/190 = 111/190
I hope this helps. :-)
Hey,
The probability would be:
The total number of biscuits = 20
(plain, plain) = (12/20)(11/19) = 132/380
(chocolate,chocolate) = (5/20)(4/19) = 20/380
(ginger,ginger) = (3/20)(2/19) = 6/380
Probability (they both are of the same type) = 132/380+ 20/380 + 6/380 = 158/380 = 79/190
Probability (they were not the same type.) = 1- 79/190 = 111/190
I hope this helps. :-)
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reisamimi
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#4
why was the denominator 19 when you were working it out, if the question said they take 2 biscuits
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