Bell RingerBell Ringer1.1. A sweater was on sale of $18.79. It A sweater was on sale of $18.79. It

originally cost $25.00. What is the originally cost $25.00. What is the percent of decrease of the sweater?percent of decrease of the sweater?

2.2. A flag pole stands 12 feet tall and A flag pole stands 12 feet tall and casts a shadow 7 feet long. A casts a shadow 7 feet long. A garbage can is 4 feet tall. What is garbage can is 4 feet tall. What is the length of the garbage can’s the length of the garbage can’s shadow?shadow?

ProbabiliProbabilityty

ProbabilityProbability ProbabilityProbability: how likely it is that : how likely it is that

something will occursomething will occurP(event)P(event)

OutcomeOutcome: the result of a single : the result of a single trialtrial

EventEvent: any outcome or group of : any outcome or group of outcomesoutcomes

Sample SpaceSample Space: all the possible : all the possible outcomesoutcomes

Theoretical Theoretical ProbabilityProbability

P(event)=P(event)=

EX) P(rolling an even #)= 3/6 EX) P(rolling an even #)= 3/6 = ½= ½

EX) P(tail) = ½EX) P(tail) = ½

EX) P(rolling a 2)= 1/6EX) P(rolling a 2)= 1/6

# of favorable outcomes# of possible outcomes

Compliment of an Compliment of an EventEvent

EX) A contestant must choose one of EX) A contestant must choose one of five envelopes in which one contains five envelopes in which one contains the grand prize, a car. Find the the grand prize, a car. Find the probability of not choosing the car.probability of not choosing the car.

P(car) = 1/5P(car) = 1/5

P(not choosing the car) = 1 – P(car)P(not choosing the car) = 1 – P(car)

= 1 – 1/5= 1 – 1/5

= 4/5= 4/5

Experimental Experimental ProbabilityProbability

P(event)=P(event)=

EX) A skateboard manufacturer EX) A skateboard manufacturer inspected 1000 skateboards at inspected 1000 skateboards at random and found no defects in 992 random and found no defects in 992 skateboards. What is the probability skateboards. What is the probability that a skateboard selected at random that a skateboard selected at random had no defects?had no defects?

P(no defects) = 992/1000 = 99.2%P(no defects) = 992/1000 = 99.2%

# of times an event occurs# of times the experiment

is done