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# Lesson 29 — Activity 1: Probability

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Lesson 29 — Activity 1: Probability

#### Getting Ready

#### Probability is the chance of something happening or because of what has happened previously, the expectation that a prediction will come true.

Predicting is a part of this process.

#### Try This:

#### If you noticed the sky was clear and blue and the sun was shining, what kind of a day would you predict it will be?

#### You might predict that the weather would be very nice that day,because when the sky was blue and the sun was shining in past days, the weather was very nice as well.

#### Many events cannot be predicted with total certainty. The best we can say is how likely they are to happen. When discussing probability, we often use words such as **probable/improbable**, **likely/less likely/more likely**, and **best/worst**.

#### Let's look at this example:

#### If you toss a coin, there are two possible outcomes. The coin could land on Heads (H) or it could land on Tails (T).

We say that the probability of the coin landing on H is 1/2. We can also say that the probability of the coin landing on T is 1/2.

#### Probability doesn't tell exactly what will happen, but it is a guide. In
the coin example above, if you tossed the coin 100 times, how many times
would Heads come up? Since the probability says that Heads has a 1/2
chance of occuring, we could expect 50 times. It may actually be 48 times or 55 times, but it is **likely** to be around 50 times.

#### Probability over a period of time or for many outcomes can be estimated.

#### Probability = __the number of times an event could occur__

total number of outcomes

#### Consider the marbles shown below:

#### The total number of outcomes is five as there are five marbles. The chance of selecting a red marble each time is 1. The probability of selecting a red marble each time is 1/5. The chance of selecting a yellow marble each time is 2. The probability of selecting a yellow marble each time is 2/5.

#### What would be the probability of selecting a green marble each time?

#### The probability of selecting a green marble each time is 1/5.

#### Knowledge of probabilities can be used to make predictions about events that happen in our daily lives.

Courtesy of K&E Studio

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