**"Conditional probability"**

## Years 9 – 12 Two Aces

*By toni On 12 June, 2020 · Leave a Comment*

We have six cards, four Aces and the Jack of hearts and Queen of spades in an envelope or bag. You pick 2 cards at random and tell me “I have an Ace”. What is the probability that you have two aces?

Next suppose I pick 2 of the 6 cards at […]

## Years 9 – 12 In the Bag

*By toni On 4 August, 2017 · Leave a Comment*

You have 2 different bags of marbles.

One bag has 3 Red and 2 Blue the other has 5 Red and 3 Blue.

Mzo picks one marble from each bag at random.

What is the probability he picks one of each colour? What is the probability he does NOT pick a […]

## Years 10-12 If This Then That

*By toni On 4 August, 2017 · Leave a Comment*

In front of you there are 20 envelopes.

Eight of the envelopes each contain 5 blue and 3 red sheets of paper.

The other 12 envelopes each contain 6 blue and 2 red sheets of paper.

You choose one envelope at random. Then you choose a sheet of paper from it at […]

## Years 10 – 12 Out in the Snow

*By toni On 15 August, 2013 · Leave a Comment*

A motorist plans to drive to Cradock. Event X is that he arrives at his destination in less than 3 hours. He estimates that the probability of it snowing is 1/6 and the probability of event X if it snowed is 1/10.

What is the probability that it snows and he gets there in […]

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