There are 16 results
Broad Topics > Probability > Conditional probability
Non-transitive Dice
Age 11 to 14
Challenge Level
Alison and Charlie are playing a game. Charlie wants to go first so Alison lets him. Was that such a good idea?
At Least One...
Age 11 to 14
Challenge Level
Imagine flipping a coin a number of times. Can you work out the probability you will get a head on at least one of the flips?
Mathsland National Lottery
Age 14 to 16
Challenge Level
Can you work out the probability of winning the Mathsland National Lottery?
Same Number!
Age 14 to 16
Challenge Level
If everyone in your class picked a number from 1 to 225, do you think any two people would pick the same number?
The Birthday Bet
Age 14 to 16
Challenge Level
The next ten people coming into a store will be asked their birthday. If the prize is £20, would you bet £1 that two of these ten people will have the same birthday ?
Two's Company
Age 11 to 14
Challenge Level
Seven balls are shaken. You win if the two blue balls end up touching. What is the probability of winning?
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?
Do You Brush Your Teeth Every Day?
Age 14 to 18
Challenge Level
How can we find out answers to questions like this if people often lie?
Dropouts
Age 14 to 16 Short
Challenge Level
What percentage of students who graduate have never been to France?
Statins and Risk
Age 14 to 16
Challenge Level
"Statins cut the risks of heart attacks and strokes by 40%"
Should the Professor take statins? Can you help him decide?
How Risky is My Diet?
Age 11 to 16
Challenge Level
Newspapers said that eating a bacon sandwich every day raises the risk of bowel cancer by 20%. Should you be concerned?
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?
Penta Colour
Age 14 to 16
Challenge Level
In how many different ways can I colour the five edges of a pentagon so that no two adjacent edges are the same colour?
Fixing the Odds
Age 14 to 16
Challenge Level
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?
Coin Tossing Games
Age 14 to 16
Challenge Level
You and I play a game involving successive throws of a fair coin. Suppose I pick HH and you pick TH. The coin is thrown repeatedly until we see either two heads in a row (I win) or a tail followed by a head (you win). What is the probability that you win?
NRICH is part of the family of activities in the Millennium Mathematics Project.