SAT Math : SAT Mathematics

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #72 : How To Find The Probability Of An Outcome

Jimmy is having trouble choosing what to wear to the baseball game.  He has six shirts, three pants, two pairs of socks and three pairs of shoes.  How many different outfits does Jimmy have to choose from?

Possible Answers:

Correct answer:

Explanation:

Choosing one of each clothing item is an independent event and should be multiplied together.  So the answer becomes 

or 

different combinations.

Example Question #76 : Outcomes

Joe has eight marbles: 3 Red, 2 Green, 2 Blue and 1 Yellow.  

If Joe puts the marbles into a bag and draws out four, what are the odds that he gets exactly one of each color? 

Possible Answers:

\frac{1}{8}

\frac{7}{1680}

\frac{3}{1024}

\frac{12}{140}

\frac{1}{140}

Correct answer:

\frac{1}{140}

Explanation:

The probabilities of each pick changes as fewer marbles remain in the bag.  Each selection order of the colors will yield the same probability, expressed as:

Example Question #76 : Outcomes

If you flip a fair coin four times in a row, what is the probability of getting at least one head?

Possible Answers:

\frac{3}{8}

\frac{15}{16}

\frac{1}{4}

\frac{5}{8}

\frac{1}{16}

Correct answer:

\frac{15}{16}

Explanation:

1-P(no\ heads)=P(at\ least\ one\ heads)

There are 16 different ways to flip a fair coin four times in a row.  There is only one way to get all tails.

P(no\ heads)=\frac{1}{16}

so the P(at\ least\ one\ heads)=1-\frac{1}{16}=\frac{15}{16}

Example Question #74 : Probability

When rolling two standard six-sided dice, what is the probability of getting five or less?

Possible Answers:

\frac{7}{12}

\frac{3}{8}

\frac{5}{16}

\frac{1}{6}

\frac{5}{18}

Correct answer:

\frac{5}{18}

Explanation:

The sample space for rolling two six-sided dice is 36.

Counting the wanted outcomes gives:

2:  1,1 (1)

3: 1,2 and 2,1 (2)

4: 1,3 and 2,2 and 3,1 (3)

5: 1,4 and 2,3 and 3,2 and 4,1 (4)

So there are 10 ways to get a five or less.

Thus the probability of getting a five or less is \frac{10}{36}=\frac{5}{18}.

Example Question #3161 : Sat Mathematics

How many different ways can five books be lined up on a shelf?

Possible Answers:

225

120

75

90

25

Correct answer:

120

Explanation:

Order matters, so we use permutations:  _{5}^{5}\textrm{P}5\times 4\times 3\times 2\times 1=120.

Example Question #3162 : Sat Mathematics

You have a box of 90 colored scrunchies. Half of the scrunchies are black, one third of the scrunchies are white, one ninth of the scrunchies are blue, and the rest are green. You pull the scrunchies from the box at random.

The first scrunchie you pick up is blue. The second scrunchie is green. What is the probability that the third scrunchie you pick up will be black?

Possible Answers:

\frac{1}{2}

\frac{43}{90}

\frac{45}{88}

None of the other answers

\frac{43}{88}

Correct answer:

\frac{45}{88}

Explanation:

Half of the scrunchies are black, so

90\times \frac{1}{2}=45\hspace{1 mm}black\hspace{1 mm}scrunchies

One third of the scrunchies are white

90\times \frac{1}{3}=30\hspace{1 mm}white\hspace{1 mm}scrunchies

One ninth of the scrunchies are blue

90\times \frac{1}{9}=10\hspace{1 mm}blue\hspace{1 mm}scrunchies

And the rest are green:

90-45-30-10=5\hspace{1 mm}green\hspace{1 mm}scrunchies

If we have already drawn two, our total amount of scrunchies is now 88, so the probability of pulling a black scrunchie will be:

\frac{45}{88}

 

 

Example Question #3162 : Sat Mathematics

There is a classroom of 60 students. \frac{7}{12} of the students are wearing red shirts, \frac{1}{3} of the students are wearing pink shirts, and the rest of the students are wearing orange shirts. What is the probability of randomly selecting the name of a student wearing an orange shirt?

Possible Answers:

8.3\%

None of the available answers

\frac{1}{6}

\frac{2}{25}

\frac{1}{12}

Correct answer:

\frac{1}{12}

Explanation:

\frac{7}{12} of the students are wearing red shirts, and

\frac{7}{12}\times 60=\frac{7}{1}\times 5=35\hspace{1 mm}students

One third of the students are wearing pink shirts

\frac{1}{3}\times 60=\frac{1}{1}\times 20=20\hspace{1 mm}students

The remaining students are wearing orange

60-35-20=5\hspace{1 mm}students

The probability of randomly selecting a student wearing an orange shirt is

\frac{5}{60}=\frac{1}{12}

Example Question #3163 : Sat Mathematics

A bag of colored candies has ten red candies, 14 purple candies, 12 orange candies, and 4 yellow candies. What is the ratio of yellow to orange candies in the bag?

Possible Answers:

Correct answer:

Explanation:

There are four yellow candies, and 12 orange candies, so the raio is:

The ratio of yellow to orange candies is 1:3

Example Question #83 : Probability

 of the population in Town A is NOT Asian. In addition,  of the Asian population in Town A is male. A random person from Town A is selected. What is the probability that the person selected is both Asian and female.

Possible Answers:

Correct answer:

Explanation:

Recall:

Consequently, the probability that the person selected is Asian is:

Similarly, the probability that a randomly selected Asian person is also female is:

Finally, the probability of 2 unrelated events occuring is equal to the product of the individual probabilities of the 2 events. Therefore the probability of selecting an Asian female is

Example Question #3164 : Sat Mathematics

Fred wants to put together outfits that he can wear for the day.  He can wear any type of outfit for school, but he needs to wear formal attire for dinner later.  He can either choose to wear something all day or choose to change clothes before going out to dinner.

If Fred has 2 formal shirts and 3 informal shirts, 1 pair of formal pants and 2 pairs of informal pants, and 1 pair of formal shoes and 1 pair of informal shoes, how many different ways could Fred appear for school and then dinner, allowing for changing in between?

Possible Answers:

Correct answer:

Explanation:

Fred can wear anything to school. This means he can wear either formal things or informal things.  He has 3 informal shirts and 2 formal shirts.  This means he has a total of 5 shirts to choose from when deciding what to wear.  Similarly, he has 3 pairs of pants and 2 pairs of shoes to choose from.  After choosing a shirt (5 options), he chooses pants (3 options) and shoes (2 options) resulting in  choices for outfits to wear to school.

Fred must wear formal attire to the dinner.  This means that Fred can only choose between his 2 formal shirts, his formal pair of pants, and his formal shoes.  Since he only has a choice of shirts, he ends up only having 2 choices to make in outfits.

To figure out how many ways he can dress throughout the day, we simply choose an outfit for school and an outfit for dinner.  We have 30 choices for what to wear to school and 2 choices to wear to dinner, giving us choices in total.

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