99% of people who have measles have spots. Ben has spots. Do you think he has measles?
I'd be very surprised if I had three children all with the same birthday, but I read in the paper that it happened to one family...
In 1% of cases, an HIV test gives a positive result for someone who is HIV negative. How likely is it that someone who tests positive has HIV?
Gabriel multiplied together some numbers and then erased them. Can you figure out where each number was?
How risky is your journey to school?
Are you at risk of being a victim of crime? How does your perception of that risk compare with the facts and figures?
Can you match the cards and figure out whether the tabloid headlines can be trusted?
Can you explain what is going on in these puzzling number tricks?
Where should you start, if you want to finish back where you started?
How many different differences can you make?
Can you figure out how sequences of beach huts are generated?
Can you solve the clues to find out who's who on the friendship graph?
How can you decide if a graph is traversable?
Can you find a way to connect each house to the utilities without any pipes crossing?