Probability

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Probability
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Probability is the chance that something will
occur or happen.

• Probabilities are written as fractions, decimals,
  or percents.
• Probability is always between 0 and 1.
• 0 means an event CANNOT happen
• 1 means an event will ALWAYS happen

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As likely as not
Certain
Impossible
0 0
1 100
0.5 50
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State whether each event is impossible, likely as
not, or certain to happen.

• You roll an even number on a standard number
  cube.

• February has 28 days this year.

RED
BLUE
GREEN
BLUE

• This spinner lands on blue.

• This spinner lands on an odd number.

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To find the actual probability of an event
occurring use the following formula

• what you want to have happen
• what can actually happen

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For one month, Mr. Jones recorded the time at
which his train arrived. He organized his results
in a frequency table.
Time 650 652 653 656 657 700
Frequency 7 8 5
Find the probability of the train arriving
between 657 and 700.
Find the probability of the train arriving before
657.
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• The spinner below was spun. Identify the outcome
  show.

P(dog)
dog
dog
P(hamster)
cat
hamster
P(dog or cat)
cat
dog
P(bird)
P(mammal)
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• What is the probability of rolling a number
  greater than 4 on a fair number cube?

What is the probability of rolling a factor of 6
using a fair number cube?
What is the probability of rolling a multiple of
3 using a fair number cube?
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• What is the probability of tossing a coin and not
  landing on tails?

What is the probability of rolling a number cube
and not landing on an even number?
If the probability of spinning a spinner and
landing on blue is 3/5, what is the probability
of not landing on blue?
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• A card is chosen at random. Find the probability
  of each. Write your answer as a fraction,
  decimal, and percent.

A
B
S
P (B)
Q
O
K
P (Q or R)
P (vowel)
E
R
P (consonant or vowel)
P (consonant or A)
P (T)
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• Suppose there is a 45 chance of snow tomorrow.
  What is the probability that it will not snow?
  Write this as a decimal and a fraction.

Suppose there is a 2 chance of winning the
lottery. What is the probability of not winning
the lottery written as a fraction?
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• The End!