proportionality

proportionality

Today's learning target is to be able to determine and solve a proportional relationship.

IV) Incompatible events. Contrary events:

• Definition: two events are incompatible if they cannot occur at the same time

  Ex: in experiment 2, event A: "we get 6" and event B: "we get 3" are incompatible

  Property: when two events are incompatible, the probability that one or the other will occur is equal to the sum of their probabilities

  Ex: in experiment 2, the event C: "we get 6 or we get 3" is

  p (C) = p (A) + p (B) = 16 + 16 = 13

• Definition: the opposite event of an event A is the one which occurs when A does not occur. We denote it A ("A barre")

  Ex: in experiment 2, ie event D: "we get 3". The opposite event D can be written: "we do not get 3"

  Property: the sum of the probabilities of an event A and its opposite is 1 p (A) + p (A) = 1

  15 Ex: calculate the probability of the opposite event of D, p (D) = 1 - p (D) = 1 - 6 = 6