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# Basic Probability

Introduction: Today's your class trip to the zoo. You aren't sure if you should bring a raincoat, so you check the weather forecast. The weather prediction for the day is 10% chance of rain. Do you bring your raincoat?

Let's look at the probability of rain. Probability is the measure of how likely an event will occur. Since there is a 10% chance of rain, the likelihood of rain is one out of ten. If the forecast is correct, rain is unlikely, but not impossible. You most likely won't need your raincoat, but you may want to bring it just in case.

The probability of an event occurring is a ratio of the number of outcomes that meet the condition to the total number of possible outcomes. Probability can be expressed as a fraction, decimal, or percentage. The closer the value is to zero, the less likely an event will occur. The closer the value is to one, or 100%, the greater the likelihood the event will occur. The probability of rain on the day of your class trip can be expressed as:

$P(rai n)= 1/10=0.1=10%$

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