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Sue has 20 biscuits in a tin.

There are: 12 plain biscuits
5 chocolate biscuits
3 currant biscuits
Sue takes two random biscuits from the tin.
Work out the probability that they are not the same type.

User RThomas
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1 Answer

7 votes

Answer:

The probability that the two biscuits were not the same type is 58.4%.

How much is the probability that the two biscuits were not the same type?

The probability that they are different is the opposite of the probability that they are the same.

The probability that they are the same is:

⇒ P(plain, plain) = (12/20) (11/19) = 132 / 380

⇒ P(chocolate, chocolate) = (5/20) (4/19) = 20 / 380

⇒ P(currant, currant) = (3/20) (2/19) = 6 / 380

⇒ P(same) = 132/380 + 20/380 + 6/380

⇒ P(same) = 158/380

⇒ P(same) = 79/190

Therefore, the probability that they are different is:

⇒ P(different) = 1 − 79/190

⇒ P(different) = 111/190

⇒ P(different) ≈ 58.4%

What does probability mean?

Probability means possibility. It is a branch of mathematics that deals with the occurrence of a random event.

User Juan David
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