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Probability is Everywhere


This course focuses on applying probability to games of chance. However, all of the techniques and mathematical tools we'll introduce can also be applied to many situations outside of games. Probability problems appear everywhere and every day, yet the next 5 problems in this quiz are practical cases that trick even experienced problem-solvers!

Probability in Your Daily Life

One day, the traffic light at a certain intersection is red when you reach it and no other cars are in front of you. You wait 45 seconds for it to turn green.

The next day you reach the same light and it's red again. Additionally, another car is already there, waiting for the light to change, and you pull to a stop behind him.

Which scenario is more likely to occur on the second day?

NOTE: You may assume the light changes at regular intervals and is not affected by when cars are near or based on the time of day.

Probability in Your Daily Life

Suppose you have a bag with 5 chocolate caramels and 5 cherry cordials. Your friend grabs a candy at random and eats it. Afterwards, without looking at what's left, you grab and eat one of the remaining 9 candies. What is the probability you just ate a cherry cordial?

Probability in Social Science

The world's oldest Olympic medalist was 72 years old (Oscar Swahn of Sweden). Pictured above is Amy. Which of these statements about her is more likely to be true?

Probability in Science and Health

For this puzzle, test your rapid-fire intuition by guessing without calculating, or do the calculation if you want.

Disease Z infects 1 out of every 1000 people. There's a test for Disease Z which is guaranteed to test positive for someone with the disease. For those without the disease, they will test positive 1% of the time.

You tested positive for Disease Z, and your doctor wants to place you on an expensive emergency treatment. What's the probability you actually have it?

Probability in Engineering and Product Design

The matchsticks represent fences protecting a sheep from a wolf. Note that if two of the matchsticks are removed at random, then the wolf might be able to get to the sheep.

Would moving two matchsticks from the outer ring to the inner ring, as shown below, make the sheep any safer when two matchsticks are removed at random?


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