7th Grade - Probability


If you are rolling a die and want to see your chances of getting a 6, probability can help!


  • A probability is the likelihood of a favorable or specific outcome happening.
  • A probability of an event or Outcome always ranges from 0 to 1. The closer it is to 1, the more likely that event will occur.
  • Here are a few terms to keep in mind:
    • Sample Space or Total Outcomes: All possible results of an experiment are outcomes. If you are rolling a die, the total outcomes are 6. The sample space, in this case, is 6.
    • Favorable Outcome (s): If you are looking for an even number, the total favorable outcomes are 3.
    • Event: An event is a set of some favorable or all outcomes.

Categories of Probability

There are two categories of probability.

  • Theoretical Probability

Theoretical or actual probability where all outcomes are equally likely is:

P(event) = Number of favorable outcomesTotal outcomes

  • Experimental Probability

Experimental probability is based on data collected from repeated trials or surveys.

P(event) = Number of favorable outcomes based on trial or surveyTotal outcomes

Solved Examples

1. What is the probability of getting 6 when you roll a die?

Total outcomes: 6

Favorable outcome(s): 1

P(Getting 6) = 16

2. You randomly pick a card from a deck of cards. What is the probability that it is of spade suite?

Total outcomes: 52 (52 cards in a deck)

Favorable outcome(s): 13 (13 spade cards)

P(Spades) = 1352 which is 14

Cheat Sheet

  • Probabilities are usually expressed in ab form.
  • A probability of 0 means an event can't occur.
  • A probability of 1 means the event is sure to occur.
  • Even though the probability is usually expressed as a fraction, it can be expressed as a decimal or percent.