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Usually (at the school math level) you are given a large finite set of events A and its subset of events B.
The events of A are (usually) supposed to be equally likely, and a typical question is
"what is the probability for the event from A to be the event from B ?"
In this situation, the probability is simply the ratio of numbers |B| to |A|
P(B) = ,
where |A| is the number of elements/events in the set A, while |B| is the number of elements/events in the subset B.
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To learn on how to solve elementary probability problems, look into the lessons
- Elementary Probability problems related to combinations
- A True/False test
- A shipment containing fair and defective alarm clocks
- People in a room write down integer numbers at random
- A drawer contains a mixture of socks
- Students studying foreign languages
- Probability for a computer to be damaged by viruses
- Typical probability problems from the archive
- Geometric probability problems
- Advanced probability problems from the archive
- Challenging probability problems
- Selected probability problems from the archive
- OVERVIEW of lessons on Probability
in this site.