Theoretical probability

There are 67 NRICH Mathematical resources connected to Theoretical probability
How Many Balls?
problem

How Many Balls?

Age
16 to 18
Challenge level
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A bag contains red and blue balls. You are told the probabilities of drawing certain combinations of balls. Find how many red and how many blue balls there are in the bag.
Same or Different?
problem

Same or Different?

Age
7 to 11
Challenge level
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Anna and Becky put one purple cube and two yellow cubes into a bag to play a game. Is the game fair? Explain your answer.
A Bit of a Dicey problem
problem

A Bit of a Dicey problem

Age
7 to 11
Challenge level
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When you throw two regular, six-faced dice you have more chance of getting one particular result than any other. What result would that be? Why is this?
Trick or Treat
problem

Trick or Treat

Age
7 to 11
Challenge level
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Mrs. Smith had emptied packets of chocolate-covered mice, plastic frogs and gummi-worms into a cauldron for treats. What treat is Trixie most likely to pick out?
Bipin's Choice
problem

Bipin's Choice

Age
7 to 11
Challenge level
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Bipin is in a game show and he has picked a red ball out of 10 balls. He wins a large sum of money, but can you use the information to decided what he should do next?
Chances are
problem

Chances are

Age
14 to 16
Challenge level
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Which of these games would you play to give yourself the best possible chance of winning a prize?
In a box
problem

In a box

Age
14 to 16
Challenge level
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Chris and Jo put two red and four blue ribbons in a box. They each pick a ribbon from the box without looking. Jo wins if the two ribbons are the same colour. Is the game fair?
Thank your Lucky Stars
problem

Thank your Lucky Stars

Age
14 to 16
Challenge level
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A counter is placed in the bottom right hand corner of a grid. You toss a coin and move the star according to the following rules: ... What is the probability that you end up in the top left-hand corner of the grid?
Scratch Cards
problem

Scratch Cards

Age
14 to 16
Challenge level
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To win on a scratch card you have to uncover three numbers that add up to more than fifteen. What is the probability of winning a prize?
Fixing the Odds
problem

Fixing the Odds

Age
14 to 16
Challenge level
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You have two bags, four red balls and four white balls. You must put all the balls in the bags although you are allowed to have one bag empty. How should you distribute the balls between the two bags so as to make the probability of choosing a red ball as small as possible and what will the probability be in that case?