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A bag contains 30 discs.

10 are red and 20 are blue.

- One disc is taken out at random and replaced by
**two**of the other colour. - Another disc is then taken out at random and replaced by
**two**of the other colour. - Another disc is then taken out at random.

Work out the probability that all three discs taken out are

**red**.

**Question**

27) A bag contains 30 discs.

10 are red and 20 are blue.

Work out the probability that all three discs taken out are

10 are red and 20 are blue.

- One disc is taken out at random and replaced by
**two**of the other colour. - Another disc is then taken out at random and replaced by
**two**of the other colour. - Another disc is then taken out at random.

Work out the probability that all three discs taken out are

**red**.**[3 marks]**