McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
6. Probabilities of Mutually Exclusive Events
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Exercise 26 Page 930

The sum of the probability of an event and the probability of its complement is 1.

10/13 or 76.9 %

Practice makes perfect
We are told that a card is randomly pulled from a standard deck. Recall that the experimental probability of an event measures the likelihood that the event occurs based on the actual results of an experiment. P=Times the Event Occurs/Times the Experiment Is Done We want to find the probability of selecting a card that is not a face card. Note that this is the complement of selecting a card that is a face card. The sum of the probability of an event and the probability of its complement is 1. P(Event)+P(Not event)=1

Let's start by finding the probability of selecting a face card, which will be our event. There are 52 cards in a deck, which is also the number of times the experiment is done.

In the deck, there is a total of 3 club face cards, 3 diamond face cards, 3 spade face cards, and 3 heart face cards. The sum of these values is the number of times the event occurs. 3+3+3+3= 12 face cards Now we have enough information to calculate P(Face card).
P=Times the Event Occurs/Times the Experiment Is Done
P(Face card)=12/52
P(Face card)=3/13
The experimental probability of selecting a face card is 313. Let's now find the probability of its complement, which is selecting a card that is not a face card.
P(Face card)+P(Not a face card)=1
3/13+P(Not a face card)=1
Solve for P(Not a face card)
P(Not a face card)=1-3/13
P(Not a face card)=13/13-3/13
P(Not a face card)=10/13
Convert to percent
P(Not a face card)=0.769231...
P(Not a face card)≈0.769
P(Not a face card)≈76.9 %
We found that P(Not a face card) is equal to 1013 or about 76.9 %.