Exercise 18 Page 930

We are told that a coin is flipped and that it lands either on heads or on tails.

Recall that the experimental probability of an event measures the likelihood that the event occurs based on the actual results of an experiment. P(Event)= Number of times the event occurs/Number of times the experiment is done We want to find the probability of not flipping heads. Note that this is the complement of flipping heads. 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 flipping heads on a coin, which will be our event. The number of times the event occurs is the total number of sides that are heads, 1, and the number of times the experiment is done is the total number of sides of the coin, 2. P( Heads)=1/2 l← ← lHeads Total sides The experimental probability of flipping heads is 12. Let's now find the probability of its complement, which is flipping a side of a coin that is not heads.

P(Heads)+P(Not heads)=1

Substitute

P(Heads)= 1/2

1/2+P(Not heads)=1

▼

Solve for P(Not heads)

SubEqn

LHS-1/2=RHS-1/2

P(Not heads)=1-1/2

OneToFrac

Rewrite 1 as 2/2

P(Not heads)=2/2-1/2

SubFrac

Subtract fractions

P(Not heads)=1/2

▼

Convert to percent

WriteDec

Write as a decimal

P(Not heads)=0.5

WritePercent

Convert to percent

P(Not heads)=50 %

We found that P(Not heads) is 12, which can be also written as 50 %.