Probability

problem
How many balls?

Age

16 to 18

Challenge level

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.
problem
396

Age

14 to 16

Challenge level

The four digits 5, 6, 7 and 8 are put at random in the spaces of the number : 3 _ 1 _ 4 _ 0 _ 9 2 Calculate the probability that the answer will be a multiple of 396.
problem
Same or different?

Age

7 to 11

Challenge level

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.
problem
A bit of a dicey problem

Age

7 to 11

Challenge level

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?
problem
Trick or treat

Age

7 to 11

Challenge level

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?
problem
Bipin's choice

Age

7 to 11

Challenge level

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?
problem
Racing odds

Age

11 to 14

Challenge level

In a race the odds are: 2 to 1 against the rhinoceros winning and 3 to 2 against the hippopotamus winning. What are the odds against the elephant winning if the race is fair?
problem
Chances are

Age

14 to 16

Challenge level

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

Age

14 to 16

Challenge level

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?
problem
Master minding

Age

11 to 14

Challenge level

Your partner chooses two beads and places them side by side behind a screen. What is the minimum number of guesses you would need to be sure of guessing the two beads and their positions?