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This quarter, there is a 50% chance that Jason will pass Accounting, a 60% chance that he will pass English, and 80% chance that he will pass at least one of these two courses. What is the probability that he will pass both Accounting and English?

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The following table shows the distribution of Democratic and Republican U.S. Senators by gender.

MALES(M) FEMALES(F) TOTAL
DEMOCRATS(D) 39 4 43
REPUBLICANS(R) 52 5 57
TOTALS 91 9 100

Use this table to determine the following probabilities.

P M   and  D size 12{P left (M" and "D right )} {}
39 / 100 size 12{"39"/"100"} {}
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P F   and   R size 12{P left (F" and "R right )} {}
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P M   or  D size 12{P left (M" or "D right )} {}
95 / 100 size 12{"95"/"100"} {}
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P F   or   R C size 12{P left (F" or "R rSup { size 8{C} } right )} {}
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P M C   or  R size 12{P left (M rSup { size 8{C} } " or "R right )} {}
61 / 100 size 12{"61"/"100"} {}
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P M   or   F size 12{P left (M" or "F right )} {}
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Again, use the addition rule to determine the following probabilities.

If P E = . 5 size 12{P left (E right )= "." 5} {} and P F = . 4 size 12{P left (F right )= "." 4} {} and E size 12{E} {} and F size 12{F} {} are mutually exclusive, find P E   and   F size 12{P left (E" and "F right )} {} .

0

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If P E = . 4 size 12{P left (E right )= "." 4} {} and P F = . 2 size 12{P left (F right )= "." 2} {} and E size 12{E} {} and F size 12{F} {} are mutually exclusive, find P E   or  F size 12{P left (E" or "F right )} {} .

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If P E = . 3 size 12{P left (E right )= "." 3} {} and P E   or   F = . 6 size 12{P left (E" or "F right )= "." 6} {} and P E   and   F = . 2 size 12{P left (E" and "F right )= "." 2} {} , find P F size 12{P left (F right )} {} .

0.5

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If P E = . 4 size 12{P left (E right )= "." 4} {} , P F = . 5 size 12{P left (F right )= "." 5} {} and P E   or  F = . 7 size 12{P left (E" or "F right )= "." 7} {} , find P E   and  F size 12{P left (E" and "F right )} {} .

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Calculating probabilities using tree diagrams and combinations

Two apples are chosen from a basket containing five red and three yellow apples. Draw a tree diagram below, and find the following probabilities.

P both red size 12{P left ("both red" right )} {}
20 / 56 size 12{"20"/"56"} {}
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P one red, one yellow size 12{P left ("one red, one yellow" right )} {}
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P both yellow size 12{P left ("both yellow" right )} {}
6 / 56 size 12{6/"56"} {}
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P First red and second yellow size 12{P left ("First red and second yellow" right )} {}
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A basket contains six red and four blue marbles. Three marbles are drawn at random. Find the following probabilities using the method shown in [link] . Do not use combinations.

P All three red size 12{P left ("All three red" right )} {}
1 / 6 size 12{1/6} {}
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P two red, one blue size 12{P left ("two red, one blue" right )} {}
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P one red, two blue size 12{P left ("one red, two blue" right )} {}
3 / 10 size 12{3/"10"} {}
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P first red, second blue, third red size 12{P left ("first red, second blue, third red" right )} {}
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Three marbles are drawn from a jar containing five red, four white, and three blue marbles. Find the following probabilities using combinations.

P all three red size 12{P left ("all three red" right )} {}
10 / 220 size 12{"10"/"220"} {}
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P two white and 1 blue size 12{P left ("two white and 1 blue" right )} {}
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P none white size 12{P left ("none white" right )} {}
56 / 220 size 12{"56"/"220"} {}
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P at least one red size 12{P left ("at least one red" right )} {}
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A committee of four is selected from a total of 4 freshmen, 5 sophomores, and 6 juniors. Find the probabilities for the following events.

At least three freshmen.

45 / 1365 size 12{"45"/"1365"} {}
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All four of the same class.

21 / 1365 size 12{"21"/"1365"} {}
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Not all four from the same class.

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Exactly three of the same class.

324 / 1365 size 12{"324"/"1365"} {}
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More juniors than freshmen and sophomores combined.

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Five cards are drawn from a deck. Find the probabilities for the following events.

Two hearts, two spades, and one club.

79092 / 2, 598 , 960 size 12{"79092"/2,"598","960"} {}
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A flush of any suit(all cards of a single suit).

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A full house of nines and tens(3 nines and 2 tens).

24 / 2, 598 , 960 size 12{"24"/2,"598","960"} {}
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A pair of nines and tens.

1, 584 / 2, 598 , 960 size 12{1,"584"/2,"598","960"} {}
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Do the following birthday problems.

If there are five people in a room, what is the probability that no two have the same birthday?

0.973

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If there are five people in a room, what is the probability that at least two people have the same birthday?

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Conditional probability

Do the following problems using the conditional probability formula: P A B = P A B P B size 12{P left (A \lline B right )= { {P left (A intersection B right )} over {P left (B right )} } } {} .

A card is drawn from a deck. Find the conditional probability of P a queen a face card size 12{P left ("a queen " \lline " a face card" right )} {} .

4 / 12 size 12{4/"12"} {}
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A card is drawn from a deck. Find the conditional probability of P a queen a club size 12{P left ("a queen " \lline " a club" right )} {} .

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A die is rolled. Find the conditional probability that it shows a three if it is known that an odd number has shown.

1 / 3 size 12{1/3} {}
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If P A = . 3 size 12{P left (A right )= "." 3} {} and P B = . 4 size 12{P left (B right )= "." 4} {} , and P A   and  B = . 12 size 12{P left (A" and "B right )= "." "12"} {} , find the following.

  1. P A B size 12{P left (A \lline B right )} {}

  2. P B A size 12{P left (B \lline A right )} {}

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Source:  OpenStax, Applied finite mathematics. OpenStax CNX. Jul 16, 2011 Download for free at http://cnx.org/content/col10613/1.5
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