whos preparing for SAT december?

me. my current highscore is 1160 can i make it to 1400 by december??

why is the answer for the fraction question 7/18 instead of 7/25

THe queston is: What fraction of classmates who do not own a skateboard also do not own a bike? whenever you see question asked for a fraction, Easiest way is devide question for the fraction they are asking for. For example they are asking for a fraction in the above question. So We need to devide the question Devide= Who do not own a skateboard / Do not own a bike so Fraction is 7/18 It's a tricky way to answer these types of question.

I feel hard to comprehend the last one "Rhesus factor".

3 (probability of O) is equal to half. In probability, The total is always equal to 1. The total here is six (3 being half) So that means the total of the others is also 3. 2 are one each. one left

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Course: Digital SAT Math > Unit 3

Lesson 8: Probability and relative frequency: foundations

Probability and relative frequency | Lesson

Google Classroom

A guide to probability and relative frequency on the digital SAT

What are probability and relative frequency problems?

The SAT will ask you to calculate probabilities and relative frequencies using data from two-way frequency tables.

Two-way frequency tables include two qualitative variables, one represented by rows and the other represented by columns. For example, the table below summarizes the concert attendance of students in Dr. Romelle and Dr. Yukevich's classes. The two variables are class and concert attendance.

	Attended concert	Did not attend concert	Total
Dr. Romelle's class	$17$ ‍	$14$ ‍	$31$ ‍
Dr. Yukevich's class	$23$ ‍	$10$ ‍	$33$ ‍
Total	$40$ ‍	$24$ ‍	$64$ ‍

In this lesson, we'll learn to:

Read two-way frequency tables
Use two-way frequency tables to calculate probabilities and relative frequencies
Use probabilities and relative frequencies to find missing values

You can learn anything. Let's do this!

How do I read two-way frequency tables?

The biggest challenge of table data problems is understanding what the question is asking for. Let's describe some of the values in the table below.

	Attended concert	Did not attend concert	Total
Dr. Romelle's class	$17$ ‍	$14$ ‍	$31$ ‍
Dr. Yukevich's class	$23$ ‍	$10$ ‍	$33$ ‍
Total	$40$ ‍	$24$ ‍	$64$ ‍

The number

17

is in the row "Dr. Romelle's class" and the column "attended concert". We can make a few similar statements using the number

17

$17$ ‍ students both attended the concert and are from Dr. Romelle's class.
$17$ ‍ students from Dr. Romelle's class attended the concert.
$17$ ‍ of the students who attended the concert are from Dr. Romelle's class.

The number

40

is the total for the column "attended concert". This means

40

students (from both Dr. Romelle and Dr. Yukevich's classes) attended the concert.

Similarly, the number

33

is the total for the row "Dr. Yukevich's class". This means there are

33

students in Dr. Yukevich's class (some attended the concert, some did not).

The number

64

in the lower right corner is total number of students for all categories.

Try it!

Try: identify values based on their descriptions

	Owns a skateboard	Does not own a skateboard	Total
Owns a bike	$4$ ‍	$11$ ‍	$15$ ‍
Does not own a bike	$3$ ‍	$7$ ‍	$10$ ‍
Total	$7$ ‍	$18$ ‍	$25$ ‍

Jackie asked his classmates whether they own a bike or a skateboard. The results are shown in the table above.

How many classmates own both a bike and a skateboard?

How many classmates own skateboards?

How many classmates own either a bike or a skateboard, but not both?

How do I calculate probabilities and relative frequencies using two-way frequency tables?

Once we correctly identify the values we're looking for in a problem, the rest of the problem is basically dividing two values to find a fraction, percentage, or probability.

Note: While probabilities and relative frequencies are different concepts, we perform the same calculations for them.

Let's use the table below for some example calculations!

	Attended concert	Did not attend concert	Total
Dr. Romelle's class	$17$ ‍	$14$ ‍	$31$ ‍
Dr. Yukevich's class	$23$ ‍	$10$ ‍	$33$ ‍
Total	$40$ ‍	$24$ ‍	$64$ ‍

What fraction of Dr. Romelle's class did not attend the concert?

What percent of students from both classes attended the concert?

If a student from both classes is selected at random, what is the probability that the student is from Dr. Yukevich's class and attended the concert?

There are a total of

64

students from both classes.

23

of these

64

students are both from Dr. Yukevich's class and attended the concert.

The probability of randomly selecting a student who's both from Dr. Yukevich's class and attended the concert is equal to the fraction of students who are both from Dr. Yukevich's class and attended the concert out of all students.

The probability is $\frac{23}{64}$ ‍.

Try it!

Try: calculate a probability and a relative frequency

	Owns a skateboard	Does not own a skateboard	Total
Owns a bike	$4$ ‍	$11$ ‍	$15$ ‍
Does not own a bike	$3$ ‍	$7$ ‍	$10$ ‍
Total	$7$ ‍	$18$ ‍	$25$ ‍

Jackie asked his classmates whether they own a bike or a skateboard. The results are shown in the table above.

If a classmate is selected at random, what is the probability that they do not own a bike? (Enter your answer as a fraction or decimal between

0

and

1

What fraction of classmates who do not own a skateboard also do not own a bike? (Enter your answer as a fraction between

0

and

1

How do I find missing values in a table?

Note: missing value questions appear very rarely on the SAT.

Just as we can calculate a probability or relative frequency using the values in two-way frequency tables, we can calculate missing values in a table when given a probability or relative frequency.

Some two-way frequency tables do not provide the totals for us. For these tables, it's helpful to add a row and a column for the totals.

Let's look at another example using the students in Dr. Romelle and Dr. Yukevich's classes.

	Plays an instrument	Does not play an instrument	Total
Dr. Romelle's class	$20$ ‍	$11$ ‍	$31$ ‍
Dr. Yukevich's class			$33$ ‍
Total			$64$ ‍

\frac{3}{4}

of the students in the two classes play an instrument, how many students in Dr. Yukevich's class play an instrument?

There are

64

total students in the two classes, and

\frac{3}{4}

64

48

. This is the total for the column "plays an instrument".

Since we know

20

students in Dr. Romelle's class play an instrument, the number of students who play instruments in Dr. Yukevich's class is

48 - 20 = 28

	Plays an instrument	Does not play an instrument	Total
Dr. Romelle's class	$20$ ‍	$11$ ‍	$31$ ‍
Dr. Yukevich's class	$28$ ‍		$33$ ‍
Total	$48$ ‍		$64$ ‍

$28$ ‍ students in Dr. Yukevich's class play an instrument.

Try it!

try: find missing values in a table

	B or better	C or worse
Finished book	$8$ ‍	$1$ ‍
Did not finish book

The table above shows the grades of

20

students who wrote an essay based on a book. Some of the values are missing.

How many students did not finish the book?

50 %

of the students received a B or better on the essay, how many of those students did not finish the book?

Your turn!

Practice: calculate a probability

	Watches gaming livestreams	Does not watch gaming livestreams	Total
Plays video games	$44$ ‍	$65$ ‍	$109$ ‍
Does not play video games	$3$ ‍	$39$ ‍	$42$ ‍
Total	$47$ ‍	$104$ ‍	$151$ ‍

Barento surveyed

151

high school students on their video game-related activities. The results are summarized in the table above. If one student from the survey is selected at random, what is the probability that the selected student does not play video games and does not watch gaming livestreams?

Practice: calculate a relative frequency

	Great Britain	United States	Other nations	Total
Gold	$56$ ‍	$23$ ‍	$31$ ‍	$110$ ‍
Silver	$51$ ‍	$12$ ‍	$44$ ‍	$107$ ‍
Bronze	$39$ ‍	$12$ ‍	$56$ ‍	$107$ ‍
Total	$146$ ‍	$47$ ‍	$131$ ‍	$324$ ‍

The table above represents the medals won at the

1908

Summer Olympics. Approximately what percent of gold medals were won by Great Britain and the United States?

Practice: calculate a missing value

**Blood Type**
Rhesus factor	$A$ ‍	$B$ ‍	$AB$ ‍	$O$ ‍
$+$ ‍	$77$ ‍	$76$ ‍	$19$ ‍	$122$ ‍
$-$ ‍	$1$ ‍	$x$ ‍	$1$ ‍	$3$ ‍

Human blood can be classified into four common blood types—

A

B

AB

, and

O

. It is also characterized by the presence

(+)

or absence

(-)

of the rhesus factor. The table above shows the distribution of blood type and rhesus factor for a group of people. If one of these people who is rhesus negative

(-)

is chosen at random, the probability that the person has blood type

O

\frac{1}{2}

. What is the value of

x

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why is the answer for the fraction question 7/18 instead of 7/25
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- muntarinmim
  Posted 10 months ago. Direct link to muntarinmim's post “THe queston is: What frac...”
  THe queston is: What fraction of classmates who do not own a skateboard also do not own a bike?
  whenever you see question asked for a fraction, Easiest way is devide question for the fraction they are asking for.
  For example they are asking for a fraction in the above question.
  So We need to devide the question
  Devide= Who do not own a skateboard / Do not own a bike
  so Fraction is 7/18
  It's a tricky way to answer these types of question.
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I feel hard to comprehend the last one "Rhesus factor".
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- Hannahhhh+God=team
  Posted a year ago. Direct link to Hannahhhh+God=team's post “3 (probability of O) is e...”
  3 (probability of O) is equal to half.
  In probability, The total is always equal to 1.
  The total here is six (3 being half)
  So that means the total of the others is also 3.
  2 are one each.
  one left
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for last question:
3/5+x=1/2

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muntarinmim
Posted 10 months ago. Direct link to muntarinmim's post “Those who are finding dif...”
Those who are finding difficulties to answer the fraction asked questions-

The queston is: What fraction of classmates who do not own a skateboard also do not own a bike?
whenever you see question asked for a fraction, Easiest way is devide question for the fraction they are asking for.
For example they are asking for a fraction in the above question.
So We need to devide the question
Devide= Who do not own a skateboard / Do not own a bike
so Fraction is 7/18
It's a tricky way to answer these types of question.
Button navigates to signup pageComment on muntarinmim's post “Those who are finding dif...”
(7 votes)
Answer