Find the probability

key notes :

Definition of Probability

  • Probability is the chance or likelihood of an event happening.
  • It is measured using numbers between 0 and 1 (or as a fraction, decimal, or percentage).

Basic Probability Formula

Probability = Number of Favorable Outcomes / Total Number of Possible Outcomes

  • Example: The probability of rolling a 3 on a 6-sided die is 1/6.

Types of Probability

  • Certain Event (1 or 100%): An event that will definitely happen (e.g., The sun rising tomorrow).
  • Impossible Event (0 or 0%): An event that cannot happen (e.g., Rolling a 7 on a 6-sided die).
  • Likely Event: An event that has a high chance of occurring (e.g., Picking a red ball from a bag that mostly contains red balls).
  • Unlikely Event: An event that has a low chance of occurring (e.g., Getting heads 10 times in a row when flipping a coin).

Probability on a Number Line

  • 0 → Impossible
  • 1/2 (0.5 or 50%) → Even Chance
  • 1 → Certain

Examples in Real Life

  • Flipping a coin (heads or tails)
  • Rolling a die (numbers 1 to 6)
  • Drawing a card from a deck
  • Choosing a random marble from a bag

Experimental vs. Theoretical Probability

  • Theoretical Probability: Based on mathematical calculations (e.g., probability of rolling a 4 on a die is 1/6).
  • Experimental Probability: Based on actual trials (e.g., flipping a coin 10 times and getting heads 6 times → experimental probability = 6/10 or 0.6).

Using Probability in Games

  • Probability helps in making predictions and understanding chances in board games, dice games, and card games.

Learn with an example

🌀 If you flip a coin, what is the probability that it will land on tails?

Write your answer as a fraction or a whole number. With fractions, use a forward slash ( / ) to separate the numerator and denominator. _____

There are 2 possible outcomes: heads or tails.

There is 1 favorable outcome: tails.

The probability is 1 out of 2, or 1/2.

🌀 If you roll a 6-sided die, what is the probability of rolling an odd number?

Write your answer as a fraction or a whole number. With fractions, use a forward slash ( / ) to separate the numerator and denominator. ______

There are 6 possible outcomes: 1, 2, 3, 4, 5, 6.

There are 3 favorable outcomes: 1, 3, 5.

The probability is 3 out of 6, or 3/6.

🌀 If you roll a 6-sided die, what is the probability of rolling a four?

Write your answer as a fraction or a whole number. With fractions, use a forward slash ( / ) to separate the numerator and denominator. ______

There are 6 possible outcomes: 1, 2, 3, 4, 5, 6.

There is 1 favorable outcome: 4.

The probability is 1 out of 6, or 1/6.

Let’s practice!🖊️