Finding missing values inside of a table using data from other fields of the table

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Table data

Table data on the SAT test

SAT Subscore: Problem solving and data analysis

Studying table data

On the SAT test table data topic is part of problem solving and data analysis subscore that includes 9 advanced topics (see the full topics list on the top menu). 

Table data topic is the fifth topic of problem solving and data analysis subscore. Start learning problem solving and data analysis subscore with its first topic ratios, rates and proportions  and its second topic percentages.

Table data topic is divided into sections from easy to difficult (the list of the sections appears on the left menu). Each section includes detailed explanations of the required material with examples followed by a variety of self-practice questions with solutions.

Finish studying heart of algebra subscore topics before you study this topic or any other problem solving and data analysis subscore topic. (Heart of algebra subscore includes basic algebra topics which knowledge is required for understanding problem solving and data analysis subscore topics). 

Table data- summary

A frequency table is a table that shows the number of times the items occur.

A two- way frequency table displays frequencies for two variables so that one variable is represented by rows and the other variable is represented by columns.

To calculate a ratio from a two- way frequency table we need to find the 2 relevant values in the table and divide them. If possible, simplify the result.

To calculate a percentage from a two- way frequency table we need to find the 2 relevant values in the table and plug them into the percentage formula.

To calculate a probability from a two- way frequency table we need to find the 2 relevant values in the table and divide them.

We can find missing values in tables:
Finding the total of a table.
Finding missing values inside of a table using data from other fields of the table
Finding missing values inside the table using a given ratio or probability value.

Continue reading this page for detailed explanations and examples.

Reading two- way frequency tables

Identify the name of the variable in the rows and the columns and the total values that are summed in the rows and the columns (if exist).

For example:
The table below shows the number of students that passed and failed the exam in two classes.

                   Class 1       Class 2      Total
Passed           20               15             35
Failed              10               15             25
Total                30               30             60

After reading the table we can see that:
There are 30 students in each class and 60 students in both classes.
The number of students that passed the exam in both classes is 35.
From the students that passed the exam there are 15 students from class 2.
There are 10 students that failed the exam and study in class 1.

Consider the following example:

The table below shows the number of students that passed and failed science and math exams in the class.

                              Passed science     Failed science      Total

Passed math                 10                           8                      18

Failed math                    7                            5                      12

Total                               17                          13                      30

How many students failed both exams?

How many students passed the math exam?

How many students passed only one exam (not both)?

How many students are in the class?

Calculating the number of students that failed both exams:
The number of students that failed both exams in written in the table and it is 10.

Calculating the number of students that passed the math exam:
The number of students that passed the math exam in written in the table and it is 18 (the total column). It is divided into 10 students that passed the science exam and 8 students that failed the science exam.

Calculating the number of students that passed only one exam (not both):
The number of students that passed only one exam is divided into students that passed the math exam and failed the science exam (8 students) and students that passed the science exam and failed the math exam (7 students). The number of students that passed only one exam is 8+7=15 students.

Note that we can calculate the number of students that passed only one exam by subtracting the number of students that failed both exams (5 students) and the number of students that passed both exams (10 students) from the total number of students (30 students) getting 30-10-5=15 students.

Calculating ratios, percentages and probabilities from two- way frequency tables

In these questions we need to find a data inside a table and then use it to calculate ratios, percentages and probabilities.

Before learning how to use tables you need to master the subjects of ratios, percentages and probabilities:

Ratios subject was explained on ratios, rates and proportions page.

Percentages subjects was explained on percentages page.

Calculating ratios from two- way frequency tables

A ratio is a comparison of two numbers, represented by a division of their amounts. The ratio between a and b can be represented as a fraction a/b. For example: The number of girls in the class is 22 and the number of boys in the class is 11. The ratio of boys to the total in the class is 11/33=1/3.

To calculate a ratio from a two- way frequency table we need to find the 2 relevant values in the table and divide them. If possible, simplify the result.

For example:

The table below shows the number of students that passed and failed the exam in two classes.

                  Class 1       Class 2      Total

Passed           20               15             35

Failed              10               15             25

Total                30               30             60

After reading the table we can see that:

The fraction of the students that failed the exam study in class 1 is:
We need to calculate the ratio of the students in class 1 that failed the exam from the total students that failed the exam.
The denominator is the number of students that failed the exam, we see in the table that 25 students failed the exam.
The numerator is the number of students that study in class 1 and failed the exam, we see in the table that 10 students study in class 1 and failed the exam.
The fraction is 10/25=2/5.

The ratio of students that study in class 1 from the total number of students is:
The denominator is the number of students in 2 classes, we see in the table that it is 60 students.
The numerator is the number of students that study in class 1, we see in the table that it is 30 students.
The ratio of the students that study in class 1 from the total numbers of students is 30/60=1/2.

The ratio of students that study in class 1 and passed the exam from the number of students that study in class 2 and passed the exam is:
The denominator is the number of students that study in class 2 and passed the exam, we see in the table that it is 15 students.
The numerator is the number of students that study in class 1 and passed the exam, we see in the table that it is 20 students.
The ratio is 20/15=4/3.

Consider the following example:

The table below shows the number of students that passed and failed the science and math exams in the class.

                              Passed science     Failed science      Total

Passed math                 10                           8                      18

Failed math                    7                            5                       12

Total                               17                         13                       30

What fraction of the students that failed science also failed math?

What fraction of the students that passed math passed science?

What is the ratio of students that passed both math and science from the total number of students?

Calculating what fraction of the students that failed science also failed math:
We need to calculate the ratio of the students that failed both science and math from the number of students that failed science.
The denominator is the number of students that failed science, we see in the table that it is 13 students.
The numerator is the number of students that failed both science and math, we see in the table that it is 5 students.
The fraction is 5/13.

 Calculating what fraction of the students that passed math passed science:
We need to calculate the ratio of the number of students that passed both math and science from the number of students that passed math.
The denominator is the number of students that passed math, we see in the table that it is 18 students.
The numerator is the number of students that passed both math and science, we see in the table that it is 10 students.
The fraction is 10/18=5/9.

Calculating the ratio of students that passed both math and science from the total number of students:
The numerator is the number of students that passed both math and science, we see in the table that it is 10 students.
The denominator is the total number of students, we see in the table that it is 30.
The ratio of students that passed both math and science from the total number of students is 10/30=1/3.

Calculating percentages from two- way frequency tables

A percentage is a number or a ratio expressed as a fraction of 100 and represents a part to whole relationship.

A percentage formula is:

percentage= 100 *  the value to be expressed
                                   _________________________
                                                   total

To calculate a percentage from a two- way frequency table we need to find the 2 relevant values in the table and plug them into the percentage formula.

For example:

The table below shows the number of students that passed and failed the exam in two classes.

                   Class 1       Class 2      Total
Passed           20               15             35
Failed             10               15             25
Total               30               30             60

After reading the table we can calculate that:

The percentage of students from class 2 that passed the exam is:
The total is the number of students that passed the exam, we see in the table that it is 35 students. The value to be expressed is the number of students that study in class 2 and passed the exam, we can see in the table that it is 15 students.

percentage = 100 *  the value to be expressed           =             15            =   43%
                                     _________________________                  ____________
                                                  total                                                  35

The percentage of students that failed the exam is:
The total is the number of students in both classes, we see in the table that it is 60 students. The value to be expressed is the number of students that failed the exam, we see in the table that it is 25 students.

percentage = 100 *  the value to be expressed           =             25             =   42%
                                   __________________________                  ____________
                                                       total                                             60

Consider the following example:

The table below shows the number of students that passed and failed the science and math exams in the class.

                              Passed science     Failed science      Total

Passed math                 10                           8                      18

Failed math                    7                            5                       12

Total                               17                          13                      30

What percent of students passed both exams?

What percent of students passed at least one exam?

Calculating what percent of students passed both exams:

The total is the number of students in the class, we see in the table that it is 30 students. The value to be expressed is the number of students that passed both exams, we see in the table that it is 10 students.

percentage = 100 *  the value to be expressed    =   10    =  33%                                                                                                               __________________________     ______
                                                   total                                30 

Calculating what percent of students passed at least one exam:

The total is the number of students in the class, we see in the table that it is 30 students. The value to be expressed is the number of students that passed at least one exam. The number of students that passed at least one exam is the students that passed only math (8 students) or the students that passed only science (7 students) or the students that passed both (10 students). The number of students that passed at least one exam is therefore 8+7+10=25 students.

percentage = 100 *  the value to be expressed   =   25  =   83%
                                    __________________________    ______
                                                    total                              30

Calculating probabilities from two- way frequency tables

The probability of an event is equal to the outcome of the event divided by the total outcomes.

To calculate a probability from a two- way frequency table we need to find the 2 relevant values in the table and divide them.

For example:

The table below shows the number of students that passed and failed the exam in two classes.

                  Class 1       Class 2      Total

Passed           20               15             35

Failed             10                15             25

Total               30                30             60

After reading the table we can calculate that if students are selected randomly:

The probability that a student failed the exam is:
The numerator is the outcome of the event, this is the number of students that failed the exam. We see in the table that 25 students failed the exam. The denominator is the total outcome, this is the total number of students. We see in the table that there are 60 students in two classes. The probability is equal to 25/60=5/12.

The probability that a student studies in class 2 and failed the exam is:
The numerator is the outcome of the event, this is the number of students that study in class 2 and failed the exam. We see in the table that 15 students study in class 2 and failed the exam. The denominator is the total outcome, this is the total number of students. We see in the table that there are 60 students in two classes. The probability is equal to 15/60=1/4.

Consider the following example:

The table below shows the number of students that passed and failed the science and math exams in the class.

                              Passed science     Failed science      Total

Passed math                 10                           8                      18

Failed math                    7                            5                      12

Total                               17                         13                      30

If students are selected randomly, what is the probability that a student passed both exams?

If students are selected randomly, what is the probability that a student failed only the science exam?

Calculating the probability that a student passed both exams:
The numerator is the outcome of the event, this is the number of students that passed both exams. We see in the table that 10 students passed both exams. The denominator is the total outcome, this is the total number of students. We see in the table that there are 30 students in the class. The probability is equal to 10/30=1/3.

Calculating the probability that a student failed only the science exam:
The numerator is the outcome of the event, this is the number of students that failed only the science exam. We see in the table that 10 students passed the math exam and failed the science exam. The denominator is the total outcome, this is the total number of students. We see in the table that there are 30 students in the class. The probability is equal to 10/30=1/3.

Finding missing values in a two- way frequency table

In these questions we are required to perform 3 tasks:
Finding the total of a table.
Finding missing values inside of a table using data from other fields of the table
Find missing values inside the table using a given ratio or probability value.

Calculating totals of a table

We can calculate the total of a row or a column of the table if we are given the values inside the row or inside the column.

The table below shows the number of students that passed and failed the science and math exams in the class.

                              Passed science     Failed science      

Passed math                 10                           8                      

Failed math                    7                             5                      

We can calculate the total of a row and a column of the table if we have the values inside the row or inside the column, getting the following table:

                               Passed science     Failed science      Total

Passed math                 10                           8                        18

Failed math                    7                            5                         12

Total                               17                         13                        30

Calculating values inside of a table using data from other fields of the table

Each row and column have inner numbers and their sum, therefore we can find a missing value if we are given all the other values in a row or a column.  

The table below shows the number of students that passed and failed the science and math exams in the class.

                          Passed science     Failed science      Total

Passed math                                                                         18

Failed math                    7                                                      12

Total                               17                            13                     30

After reading the table we can calculate that:
The number of students that failed both exams is 12-7=5.
The number of students that passed both exams is 17-7=10.
Now we can calculate the number of students that passed math and failed science: 18-10=8 or 13-5=8.

The full table is represented below:

                              Passed science     Failed science      Total

Passed math                  10                            8                     18

Failed math                      7                             5                     12

Total                                17                           13                    30

Calculating values inside of a table using data outside the table

We can calculates values inside the table if we are given additional data about their percentages or fractions.

Consider the following example:

The table below shows the number of students that passed and failed the exam in two classes.

                    Class 1       Class 2      Total

Passed                               15             

Failed                                 15             

Total                                                      60

What is the number of students that failed the exam and study in class 1 if 33.33 percent of the students passed the exam and study in class 1?

Calculating the number of students that passed the exam and study in class 1: We see in the table that there are 60 students in two classes. Since we know the total and we know the percentage, we can calculate the value to be expressed (the number of students that passed the exam and study in class 1) with the percentage formula.

percentage % = 100 *  the value to be expressed
                                         _________________________
                                                             total

33.33= 100 *  the number of students that passed the exam
                         _____________________________________________
                                                           60

The number of students that passed the exam and study in class 1= 33.33*60/100=20.

The table below shows the data including the number of students that passed the exam and study in class 1.

Class 1       Class 2      Total

Passed           20               15

Failed                                15

Total                                                    60

 

We can now calculate the total of students that passed the exam, this is 20+15=35 students.

The table below shows the data including the total of students that passed the exam.

                  Class 1       Class 2      Total

Passed           20               15             35

Failed                                 15

Total                                                     60

We can now calculate the number of students that failed the exam, it is 60-35=25 students.
We can calculate the number of students from class 1 that failed the exam, it is 25-15=10 students.

We can continue and calculate the other fields in the table:
We can calculate the number of students that study in class 1, it is 20+10=30 students.
We can calculate the number of students that study in class 2, it is 15+15=30 students.

The table below shows the data including all the calculations above:

                   Class 1       Class 2      Total

Passed           20               15             35

Failed             10                15             25

Total                30               30              60

Consider the following example:

The table below shows the number of students that passed and failed the exam in two classes.

                    Class 1       Class 2      Total

Passed                              15             

Failed          10                    

Total                                                    60

What is the number of students in class 2 that failed the exam if 1/2 of the students study in class 2?

We are given that the number of students that study in class 2 divided by the number of students in both classes is equal to 1/2. We see in the table that the total number of students in both classes is 60.

Therefore we can calculate the number of students that study in class 2:

the number of students that study in class 2             1
____________________________________________  =    _____
                                    60                                                    2

The number of students that study in class 2=60/2=30.

We can continue and calculate the other fields in the table:      
The number of students that study in class 2 and failed the exam is 30-15=15 students.
The number of the students in class 1 is 30-30=30 students.
The number of the students that passed the exam and study in class 1 is 30-10=20 students.
The number of students that passed the exam is 20+15=35 students.
The number of students that failed the exam is 10+15=25 students.

The table below shows the data including all the calculations above.

                 Class 1       Class 2       Total

Passed        20                 15              35

Failed           10                 15              25

Total             30                 30              60

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