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Session Three

Welcome to the third section of MTH140, Number bases.  In this session you will learn about the place values in the binary system as well as how to convert binary numbers in standard notation to expanded notation.

Begin this session by watching the video tape.  If you have purchased a textbook, follow along in your book. If you are using the Internet version, follow along on the webpage. If you have any difficulties, contact your instructor.  After the explanation of place values, turn off the video player and try to work the practice problems.  Once you have worked the problems, check your answers in the answer key or click on the Answer Key Links.

Section Three

Place Values In The Binary Number System

The binary number system is used in computer applications. This system is based on two digits. The digits 0 and 1 are used in the binary number system. When counting, once all of the digits have been used, a combination of digits must then be used. As digits are added, place value increases. For example, the "number" after 1 is 10. Two digits are used in the number 10; the digit placement in the number tells us the "size" of the number. The digits are used sequentially when we build numbers. The number after 11 is 100. This is because the digit on the far right has reached the maximum of value of 1 and we must begin to "reuse" values in this position.

The following numbers are the first ten numbers that we could use to count in the binary system. Zero (0) has the same value of "nothing" that we use in the decimal system. The next number would be 1, then 10, 11, 100, 101, 110, 111, 1000, 1001, and 1010. A number that contains digits other than zero or one cannot be a binary number.   For example, 456 cannot be a binary number.  The number 1001 can be a binary number since it only contains the digits one and zero.  Often times these numbers are written with a subscript to tell the reader that the numbers are binary numbers. They could be written as 12, 102, 112, 1002, 1012, 1102, 1112, 10002, 10012, and 10102 to avoid confusion.

3.1 ~ Converting from Standard Notation to Expanded Notation

Each value of a number is determined by the position of each digit in the number. The "place" of the digit has a name. In the number 1012, we refer to the position where the 1 is located on the far right hand side as the "units" place or the "two to the zero power" place. The 0 is in the "twos" place or the "two to the first power" place. The 1 on the far left is in the "fours" place or "two to the second power" place. Each additional place would be "two" to the next successive power.

The number 1012 is in standard binary notation. If we looked at the number 1012 and wrote it in a different way, we might put the information in a table such as the one shown in Table 1 ~ 3.1.

Table 1 ~ 3.1 

Digit Power of Two = Value

1

20

=

12

0

21

=

002

1

22

=

1002

Total Value

1012

Notice that numbers in the second column are all powers of two. If we wrote the number 101 without using the chart, it would be written as:

1 x 1 + 0 x 2 + 1 x 4

Another way of writing this would be:

1 x 20 + 0 x 21 + 1 x 22

We call this an expanded form.

Since the number 2 in binary notation is represented by 102, we could write the expanded notation in another way. It could be written as:

1 x 100 + 0 x 101 + 1 x 102

or putting in the subscript, it could be written as

1 x 1020 + 0 x 1021 + 1 x 1022

Notice the similarities between what has been written above and the manner in which decimal numbers are written in expanded notation. They are the same except for the subscript.

Notice that numbers in the second column are all powers of two. If we wrote the number 101 without using the chart, it would be written as:

1 x 1 + 0 x 2 + 1 x 4

Another way of writing this would be:

1 x 20 + 0 x 21 + 1 x 22

We call this an expanded form.

Since the number 2 in binary notation is represented by 102, we could write the expanded notation in another way. It could be written as:

1 x 100 + 0 x 101 + 1 x 102

or putting in the subscript, it could be written as

1 x 1020 + 0 x 1021 + 1 x 1022

Notice the similarities between what has been written above and the manner in which decimal numbers are written in expanded notation. They are the same except for the subscript.

 

Figure 3.1.1

Place Values for Binary Number 1012

1       0        1

­|      ­  |       ­ |__________1020

|        | _________________1021

|________________________1022

 

 Example: Convert 110012 to expanded notation

Solution: First, identify the value of each digit. The first digit on the right, the digit 1 is in the units or the two to the zero power place; the next digit 0, is in the twos or two to the first power place; the next digit 0, is in the fours or two to the second power place; the next digit 1 is in the eights or two to the third power place; the final digit 1 is in the sixteens or two to the fourth power place.

Table 3.1.2

Digit Power of Two = Value

1

20 or 12

=

12

0

21 or 102

=

002

0

22 or 1002

=

0002

1

23 or 10002

=

10002

1

24 or 100002

=

100002

Total Value

110012

 

If we wrote the number without using the chart, the number would be

1 x 20 + 0 x 21 + 0 x 22 + 1 x 23 + 1 x 24

The number is now in an expanded form. Since the number 2 in binary notation is represented by 102, we could write the expanded form in another way. It could be written as:

1 x 100 + 0 x 101 + 0 x 102 + 1 x 103 + 1 x 104

or putting in the subscript, it could be written as:

1 x 1020 + 0 x 1021 + 0 x 1022 + 1 x 1023 + 1 x 1024

Now the number is in expanded notation.

Figure 2 ~ 3.1

 

Place Values for Binary Number 100112

1       0        0       1        1

­|       ­ |      ­  |    ­    |    ­    | __________1020

|        |        |        |_________________1021

|        |        | ________________________1022

|        |_______________________________1023

|_______________________________________1024

3.1 ~Practice Problems

Directions: Turn off  your VCR. Change the following numbers from standard notation to expanded notation.  When you have finished working the problems, check your answers in the back of your book or click here to view the Answer Key.  Turn on your VCR to view the solutions to the practice problems worked out on the board by a teacher.

  1. 11112
  2. 1000112
  3. 102
  4. 12
  5. 101110112

 3.1 ~ Homework Problems

Directions: Turn off your VCR. Convert the following numbers from standard notation to expanded notation.  Keep your work in a notebook to be turned into your instructor at the conclusion of the course.  When you have finished working the problems, check your answers in the back of the book or click here to view the Answer Key.  If you have any questions, contact your instructor.

  1. 1002
  2. 101112
  3. 11101012
  4. 1112
  5. 1101101102
  6. 1102
  7. 111011112
  8. 1011112
  9. 1000001112
  10. 110112

Turn on your VCR and continue with this section.  If you have purchased a textbook, follow along in your book. If you are using the Internet version, follow along on the webpage. If you have any difficulties, contact your instructor.  After the explanation of converting binary numbers from expanded notation to standard notation, turn off the video player and try to work the practice problems.  Once you have worked the problems, check your answers in the answer key listed in the back of your book or click on the Answer Key Links located at the end of every section.

3.2 ~ Converting from Expanded Notation to Standard Notation

We can change numbers that have been written in expanded notation to standard notation by reversing the process. Suppose we have the notation

1 x 20 + 1 x 21 + 1 x 22 + 0 x 23 + 1 x 24

Recalling the information in Figure 1 ~ 3.1 and extending the idea, we could make a table for the powers of two in binary notation.

 

Table 1 ~ 3.2 ~ Table of Powers of 2 vs. Binary Notation

Power of 2

Binary Notation

20

12

21

102

22

1002

23

10002

24

100002

25

1000002

26

10000002

27

100000002

28

1000000002

29

10000000002

210

100000000002

We might think of our number in another way as

1 x 1020 + 1 x 1021 + 1 x 1022 + 0 x 1023 + 1 x 1024

 

Table 3.2.2

Digit Multiple of Two = Value

1

1020 (or 12)

=

12

1

1021 (or 102)

=

102

1

1022 (or 1002)

=

1002

0

1023 (or 10002)

=

00002

1

1024 (or 100002)

=

100002

Total Value

101112

Adding these values together, we get 101112 in standard notation.

Example: Convert 1 x 1020 + 1 x 1021 + 0 x 1022 + 1 x 1023 + 0 x 1024 + 1 x 1025 to standard notation.

Solution: If we follow the rules of order of operations, we must first evaluate the powers of two.

1 x 12 + 1 x 102 + 0 x 1002 + 1 x 10002 + 0 x 100002 + 1 x 1000002

Next, we perform the multiplication.

12 + 102 + 0002 + 10002 + 000002 + 1000002

Finally, we add the numbers together to obtain the sum:

1010112

which is the number in standard form.

3.2 ~ Practice Problems

Directions: Turn off your VCR.  Change the following numbers from expanded notation to standard notation.  Check your answers in the Answer Key.  Turn on your VCR to view the solutions to the problems below.

  1. 1 x 1020 + 1 x 1021 + 1 x 1022
  2. 1 x 1020 + 0 x 1021 + 0 x 1022 + 1 x 1023 + 1 x 1024
  3. 1 x 1020 + 1 x 1021 + 1 x 1022 + 1 x 1024
  4. 0 x 1020 + 1 x 1021
  5. 1 x 1020
  6. 6. 1 x 1021 + 1 x 1022 + 0 x 1023 + 0 x 1024 + 1 x 1025 + 1 x 1026

3.2 ~ Homework Problems

Directions: Turn off your VCR.  Convert the following numbers from expanded notation to standard notation.  Check your answers in the Answer Key.

  1. 1 x 1020 + 1 x 1021 + 0 x 1022 + 1 x 1023
  2. 1 x 1020 + 1 x 1021 + 1 x 1023 + 1 x 1025
  3. 1 x 1021
  4. 1 x 1020 + 0 x 1021 + 0 x 1022 + 0 x 1023 + 1 x 1024
  5. 1 x 1020
  6. 1 x 1020 + 1 x 1021 + 1 x 1022 + 0 x 1023 + 0 x 1024 + 1 x 1025 + 1 x 1026
  7. 1 x 1020 + 1 x 1021 + 1 x 1024
  8. 1 x 1022 + 1 x 1023 + 1 x 1024 + 1 x 1025
  9. 1 x 1023 + 1 x 1024
  10. 1 x 1027

 

 Turn on your VCR and continue with this section.  If you have purchased a textbook, follow along in your book. If you are using the Internet version, follow along on the webpage. If you have any difficulties, contact your instructor.  After the explanation of adding binary numbers, turn off the video player and try to work the practice problems.  Once you have worked the problems, check your answers in the answer key listed in the back of your book or click on the Answer Key Links located at the end of every section.

3.3 ~ Adding Numbers in Binary Notation

Addition in base two is very similar to addition in base ten. The first step is learning the addition facts for base two. Since there are only two digits used in the binary system, there are only three different mathematics facts that we must know. When we add any two digits together and their sum is less than the decimal number two, the sum is the same in both bases. The first two facts in the binary system are the same as in the decimal system, that is 0 + 0 = 0 and 0 + 1 = 1. (Of course the reflexive property addition holds so that 1 + 0 = 1.) We know that the equivalent of the decimal number 2 is the binary value 102. Consequently, 1 + 1 = 10 in base two. As with addition base ten, a table can provide easy reference to the addition facts in base two. We can refer to the addition table for base two depicted in Table 1 ~ 3.1 as we work our examples.

Table 1 ~ 3.1 Addition Table Base Two (Binary System)

+

0 1
0 0 1
1 1 10

 

Example 1: Add: 102 + 1002

Solution: The first step is to "line up" the digits, like we do for decimal numbers. We want to make sure that all of the digits in the same place value are beneath one another.

     102

+ 1002

We start the addition process from the right, just as if we were adding decimal numbers. We know that zero plus zero equals zero no matter what number system is being used. We can write down the zero in the units place; we have no numbers to "carry."

     102

+ 1002

        0

The next step is to add the one and the zero. The sum of one and zero is one in any number base. We write down the one in the twos place and have no numbers to carry.

     102

+ 1002

      10

The final step is to look at the two to the second power place. Since we have not carried any numbers and there is no value in the two to the second power place in the first addend, all we need to do is bring down the one to obtain the answer.

     102

+ 1002

   1102

This shows that the sum of 102 plus 1002 equals 1102 .

Example 2: Add: 1102 + 1012

Solution: The first step is to "line up" the digits, like we do for decimal numbers. We want to make sure that all of the digits in the same place value are beneath one another.

   1102

+ 1012

We start the addition process from the right, just as if we were adding decimal numbers. We know that one plus zero equals one no matter what number system is being used. We can write down the one in the units place; we have no numbers to "carry."

   1102

+ 1012

        1

The next step is to add the one and the zero. We know that their sum is one. We write down the one in the twos place and have no numbers to carry.

   1102

+ 1012

      11

The final step is to look at the two to the second power place. Since we have not carried any numbers we must just add one and one. Looking at the Table 3.3.1, we see that in the binary system 1 + 1 = 10. So, we can write 10 to obtain the answer.

   1102

+ 1012

  10112

This shows that the sum of 1102 plus 1012 equals 10112 .

Example 3: Add: 10112 + 1012

Solution: The first step is to "line up" the digits, like we do for decimal numbers. We want to make sure that all of the digits in the same place value are beneath one another.

  10112

+ 1012

We start the addition process from the right, just as if we were adding decimal numbers. We know that one plus one equals 10 from Table 3.3.1. Since there is room for only one digit in the sum line, we must begin to carry numbers. When we carry, we use the same process as the decimal system, that is, we write down the digit on the right, in the units place, and carry the digit on the left (in this case, in the twos place.) We can write down the zero in the units place and carry the one.

         1           "carried one"

  10112

+ 1012

       0

The next step is to add the one and the zero. We know that their sum is one. Now we must add the sum that we have just obtained with the "carried" one. One plus one is 10. We write down the zero in the twos place and carry the one to the two to the second place.

    1       "carried one"

  10112

+ 1012

     00

The next step is to add the zero and the one. We know that their sum is one. Now we must add the sum that we have just obtained with the "carried" one. One plus one is 10. We write down the zero in the twos place and carry the one to the two to the third place.

1       "carried one"

10112

+ 1012

    000

The final step is to look at the two to the third power place. We must add one and one to get 10. We write down the 10 to obtain the answer.

1     "carried one"

  10112

+ 1012

100002

This shows that the sum of 10112 plus 1012 equals 100002 .

Example 4: Add: 11112 + 1112

Solution: The first step is to "line up" the digits.

  11112

1112

We start the addition process from the right. One plus one is 10. We write down the zero and carry the one.

         1    "carried one"

  11112

1112

         0

The next step is to add the one and the one in the addends. We know that their sum is 10. At this point, you may wish to carry the one to the next place.

    1 1  "carried ones"

11112

+ 1112

       0

Now we must add the remaining zero with the carried one. Since 0 + 1 = 1, we write down the one in the twos place.

    1 "carried one"

11112

+ 1112

      10

The next step is to add the one and the one. We know that their sum is 10. Carry the one.

   1 1 "carried ones"

  11112

+ 1112

     10

 

Now add the zero left with the carried one to obtain a value of 1 to write in the two to the second power place.

      1 "carried one"

   11112

+    1112

       110

The final step is to look at the two to the third power place. We must add one in the first addend with the carried one to get 10. We write down the 10 to obtain the answer.

  1 "carried one"

  11112

1112

101102

This shows that the sum of 11112 plus 1112 equals 101102 .

3.3 ~ Practice Problems

Directions: Turn off your VCR.  Add the following numbers that are in binary notation. Turn the VCR back on to check your answers in the Answer Key.

  1. 1002 +102
  2. 1102 + 1012
  3. 11102 + 1112
  4. 102 + 11112
  5. 11112 + 111112

3.3 ~ Homework Problems

Directions: Turn off your VCR. Add the following numbers that are in binary notation. Check your answers in the Answer Key.  If you have any questions, contact your instructor.

  1. 1012 +1102
  2. 11102 + 11012
  3. 11102 + 11112
  4. 102 + 10112
  5. 11112 + 101112
  6. 1112 +112
  7. 1102 + 100012
  8. 111102 + 101112
  9. 102 + 1111102
  10. 11112 + 11111112

THIS CONCLUDES SESSION THREE

Last Updated January 2004

 

 

 

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