{"id":206,"date":"2017-08-22T16:29:20","date_gmt":"2017-08-22T16:29:20","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/elementary-education\/?page_id=206"},"modified":"2019-02-28T05:36:51","modified_gmt":"2019-02-28T05:36:51","slug":"numbers","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/elementary-education\/numbers\/","title":{"rendered":"Numbers"},"content":{"rendered":"<div class=\"twelve columns\" style=\"margin-top: 10%;\">\n<div class=\"advance\"><a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/number-sense\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/numbers-in-their-prime\">Next Lesson \u27a1<\/a><\/div>\n<p><!-- CONTENT BEGINS HERE --><\/p>\n<h1 id=\"title\">Numbers<\/h1>\n<h4>Objective<\/h4>\n<p>The following lessons will examine whole numbers, rational and irrational numbers, integers, and their attendant operations. We\u2019ll also review prime factorizations, divisibility rules, and other basic topics pertaining to numbers.<\/p>\n<section>\n<h3>Numbers, Numbers Everywhere<\/h3>\n<p>For some of you, it\u2019s been a long time since you\u2019ve darkened the doorway of a math classroom. And even for those of you who have a math background, it\u2019s helpful to review some of these key concepts from the ground up. So, let\u2019s start at mathematics\u2019 atomic level: numbers. Mathematicians have created a dizzying array of numbers\u2014imaginary, surreal, and transcendental, to name just a few. Fortunately for us, we only need to learn the basics. The diagram below shows the sets of numbers that we\u2019ll review here.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/numbers.jpg\" alt=\"Types of numbers\" \/><\/center>The above diagram shows the relationships among the following types of numbers: <abbr title=\"Real Numbers are the set of all rational and irrational numbers. Essentially, real numbers are all the numbers on a number line. Numbers that are not real are called imaginary numbers, but you don\u2019t need to worry about those right now.\">real numbers<\/abbr>, <abbr title=\"Rational numbers are numbers that can be written as a fraction a\/b, where a and b are integers and b \u2260 0. Rational numbers are fractions, repeating decimals, and terminating decimals. For example: 3\/5; 5; \u201327; \u20134\/17; 0.1313; 4.7623\">rational numbers<\/abbr>, <abbr title=\"Irrational numbers are numbers that cannot be written as a fraction a\/b, where a and b are integers and b \u2260 0. Irrational numbers become decimals that do not terminate or repeat. Nonperfect square roots and pi are the most commonly used irrational numbers. Example: \u221a6, -\u221a20, \u03a0, 0.23122312223...\">irrational numbers<\/abbr>, <abbr title=\"Whole numbers are the counting numbers, starting with zero. For example: 0, 1, 2, 3, 4, 5, 6...\">whole numbers<\/abbr>, and <abbr title=\"Integers are the positive and negative counting numbers, including zero. For example: \u20135, \u20134, \u20133, \u20132, \u20131, 0, 1, 2, 3, 4, 5...\">integers<\/abbr>. For example, every type of number in the diagram is a real number. Moving in, all integers and whole numbers are rational numbers and, subsequently, all whole numbers are integers. And, as you move out from the center of the diagram, the same rule holds true. Every whole number is an integer, and every integer is a rational number.<\/p>\n<p>Many numbers fit into several sets of numbers. Think about putting the number into its most restrictive set in the diagram above, and then you\u2019ll be able to see how a number can exist in more than one set.<\/p>\n<p>For example, \u20137 is a real number, rational number, and integer, but it is not a whole number because it is negative.<\/p>\n<p>What categories does \u221a18 fit into? You should be thinking irrational number and real number.<\/p>\n<p>How about \u221a9? Since the square root of 9 is 3, it fits into the categories of real number, rational number, integer, and whole number.<\/p>\n<p>Try this one on your own:<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Choose the correct statement below:<\/p>\n<ol>\n<li>No rational numbers are integers.<\/li>\n<li>All rational numbers are real numbers.<\/li>\n<li>No irrational numbers are real numbers. All integers are whole numbers.<\/li>\n<li>All integers are whole numbers.<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is B. The category of rational numbers is a subset of real numbers, as shown on the diagram. You can correct statements A and D by changing the first words to \u201csome.\u201d Correct C by making the first word \u201call.\u201d<\/p>\n<\/section>\n<p>You may be thinking the whole thing doesn&#8217;t make sense at this point. Let&#8217;s take these numbers and lay them out in a traditional way.<\/p>\n<h3>What Can You Do With a Number Line?<\/h3>\n<p>You can do more than you might have thought you could, especially if you haven\u2019t thought about it in a few years. Today, students of all ages use number lines for a wide variety of mathematical tasks, including:<\/p>\n<ul>\n<li>Counting<\/li>\n<li>Math Operations<\/li>\n<li>Measuring<\/li>\n<li>Graphing<\/li>\n<li>Estimating<\/li>\n<\/ul>\n<p>Many students want all of their number lines to start at zero, but a number line can start and end at any number.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/chadnumberline.jpg\" alt=\"Example number line\" \/><\/center>Number lines are frequently used to show the solutions to inequalities. For example: Solve x &#8211; 3 &gt; 2. The solution is x &gt; 5; any number greater than 5 makes the inequality true. Shown on the number line, it looks like this:<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/numberline_1.png\" alt=\"Solving on a number line\" width=\"50%\" \/><\/center>An empty dot shows that the number is not included in the solution.<\/p>\n<p>If the problem had been x &#8211; 3 \u2265 2, then the solution would have been x \u2265 5. On the number line, the dot on the 5 would be solid, showing that 5 is included in the solution.<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/numberline_2.png\" alt=\"Solving on a number line\" width=\"50%\" \/><\/center><\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Which point represents \u221a3?<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/chadnumberlinequestion.jpg\" alt=\"Number line question\" \/><\/center><\/p>\n<ol>\n<li>Point A<\/li>\n<li>Point B<\/li>\n<li>Point C<\/li>\n<li>Point D<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is C. The square root of 3 is approximately 1.7, so it belongs in between 1.5 and 2.<\/p>\n<\/section>\n<h3>Properties<\/h3>\n<p>The operations of addition and multiplication have a number of known properties that allow us to manipulate numbers and make the math easier. It can be challenging to remember all of these, so we have included some mnemonics to help you.<\/p>\n<table>\n<thead>\n<tr>\n<th colspan=\"3\">\n<h4>Commutative Property: ORDER<\/h4>\n<p>Remember: If you live in a community it doesn&#8217;t matter where you live in it, you are still a part of the community.<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Addition<\/td>\n<td>Order is not important when adding numbers.<\/td>\n<td>4 + 7 = 7 + 4<\/td>\n<\/tr>\n<tr>\n<td>Multiplication<\/td>\n<td>Order is not important when multiplying numbers.<\/td>\n<td>8 x 3 = 3 x 8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<table>\n<thead>\n<tr>\n<th colspan=\"3\">\n<h4>Associative Property: GROUPING<\/h4>\n<p>Remember: You spend time with your associates in a group.<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Addition<\/td>\n<td>The grouping of numbers is not important when adding numbers.<\/td>\n<td>3 + (4 + 7) = ; (3 + 4) + 7 =<\/td>\n<\/tr>\n<tr>\n<td>Multiplication<\/td>\n<td>The grouping of numbers is not important when multiplying numbers.<\/td>\n<td>2 x (8 x 3) = ; (2 x 8) x 3 =<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Neither the associative nor the commutative property works for subtraction or division. Grouping and order make a huge difference when subtracting and dividing!<\/p>\n<table>\n<thead>\n<tr>\n<th colspan=\"3\">\n<h4>Identity Property: SELF<\/h4>\n<p>Remember: The number wants to stay the same; it wants to be itself.<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Addition<\/td>\n<td>Any number plus zero equals that number.<\/td>\n<td>4 + 0 = 4<\/td>\n<\/tr>\n<tr>\n<td>Multiplication<\/td>\n<td>Any number times one equals that number.<\/td>\n<td>8 x 1 = 8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>These properties are also called the additive identity and the multiplicative identity.<\/p>\n<table>\n<thead>\n<tr>\n<th colspan=\"3\">\n<h4>Identity Property: SELF<\/h4>\n<p>Remember: The number wants to stay the same; it wants to be itself.<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Multiplication<\/td>\n<td>Any number times zero is zero.<\/td>\n<td>8 x 0 = 0<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Time for a practice question on the associative, commutative, and identity properties.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Which number sentence below illustrates the commutative property?<\/p>\n<ol>\n<li>5 x 7 x 6 = 210<\/li>\n<li>3 x (6 x 4) = (3 x 6) x 4 = 72<\/li>\n<li>4 + 5 + 0 = 9<\/li>\n<li>9 + 2 + 5 = 9 + 5 + 2 = 16<\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is D. Although there are three numbers, it is still the order of the numbers that has changed. This is the only answer choice in which the order of the numbers is different.<\/p>\n<\/section>\n<p>The last property that we\u2019ll cover is the <b>distributive property<\/b>. The distributive property combines together addition (or subtraction) and multiplication. The idea behind the distributive property is that it doesn\u2019t matter if you find the product of the sum\/difference or the sum\/difference of the product.<\/p>\n<p>Algebraically, the distributive property is represented this way:<\/p>\n<p><center><img decoding=\"async\" src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/image002.gif\" alt=\"Distributive property\" \/><\/center>The distributive property comes in handy both in algebraic problems and in solving arithmetic problems mentally. Let\u2019s try a problem:<\/p>\n<p>Can you multiply 9 x 47 in your head? Try it with the distributive property instead of replicating the paper-and-pencil mentally.<\/p>\n<p>Did you get 423? It should have worked this way:<\/p>\n<p>First thought: 9 x 40 = 360<\/p>\n<p>Second thought: 9 x 7 = 63<\/p>\n<p>Third thought: 360 + 63 = 423<\/p>\n<p>Not too hard, we hope. Try one more.<\/p>\n<p>What is 15 x 34?<\/p>\n<p>Did you get 510? Think 15(30 + 4) = (15 x 30) + (15 x 4) = 450 + 60 = 510<\/p>\n<p>In algebra, the distributive property is often used to expand or simplify <abbr title=\"In mathematics, a symbol (or combination of symbols) that represents a quantity.\">expressions<\/abbr> so that an equation can be solved. (Reversing the distributive property is called factoring, a topic that will be covered later in this module.)<\/p>\n<p>Let\u2019s see how this works in practice. We\u2019ll use the distributive property to simplify the expressions below.<\/p>\n<p>6(x + 2y)<\/p>\n<p>Distributing the 6, we arrive at 6x + 12y.<\/p>\n<p>Here is one for you to try on your own.<\/p>\n<section class=\"question\">\n<h4>Question<\/h4>\n<p>Which answer choice shows the expression correctly simplified?<\/p>\n<p>5(3<em>c<\/em> + 5<em>d<\/em>) \u2013 2<em>d<\/em><\/p>\n<ol>\n<li>15<em>c<\/em> + 23<em>d<\/em><\/li>\n<li>15<em>c<\/em> + 25<em>d<\/em><\/li>\n<li>15<em>c<\/em> + 3<em>d<\/em><\/li>\n<li>15<em>c<\/em> + 27<em>d<\/em><\/li>\n<\/ol>\n<p><a class=\"q-answer button button-primary\">Reveal Answer<\/a><\/p>\n<p class=\"q-reveal\">The correct answer is A. First distribute the 5 to the (3<em>c<\/em> + 5<em>d<\/em>), which gives you 15<em>c<\/em> + 25<em>d<\/em> (choice B). Then subtract 2<em>d<\/em> from 25<em>d<\/em>, which leaves 23<em>d<\/em>. The answer is 15<em>c<\/em> + 23<em>d<\/em>.<\/p>\n<\/section>\n<h3>Classroom Demonstration Video<\/h3>\n<p><video width=\"800\" controls><source src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/MSE01ss256-512.mp4\" type=\"video\/mp4\"><source src=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/wp-content\/uploads\/sites\/4\/2017\/08\/MSE01ss256-512.ogg\" type=\"video\/ogg\"><\/video><\/p>\n<h3>Review<\/h3>\n<p>This video demonstration shows how to use manipulatives to teach basic numbers skills.<\/p>\n<h3>Review<\/h3>\n<ul>\n<li>Numbers are grouped into sets: whole numbers, integers, rational numbers, irrational numbers, and real numbers.<\/li>\n<li>Number lines have a wide variety of purposes in many levels of mathematics.<\/li>\n<li>Math properties:\n<ul>\n<li><em>Commutative<\/em>: order of numbers is not important when adding or multiplying<\/li>\n<li><em>Associative<\/em>: grouping of numbers is not important when adding or multiplying<\/li>\n<li><em>Identity<\/em>: for addition, adding zero keeps the number the same; for multiplication, multiplying by one keeps the number the same<\/li>\n<li><em>Multiplicative Property of Zero<\/em>: anything times zero is zero<\/li>\n<li><em>Distributive<\/em>: combines addition\/subtraction and multiplication for expanding expressions with parentheses; a(b + c) = ab + ac<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/section>\n<p><!-- CONTENT ENDS HERE --><\/p>\n<div class=\"advance\"><a class=\"button\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/number-sense\">Workshop Index<\/a>\u00a0<a class=\"button button-primary\" href=\"http:\/\/americanboard.org\/Subjects\/elementary-education\/numbers-in-their-prime\">Next Lesson \u27a1<\/a><\/div>\n<p><a class=\"backtotop\" href=\"#title\">Back to Top<\/a><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Workshop Index\u00a0Next Lesson \u27a1 Numbers Objective The following lessons will examine whole numbers, rational and irrational numbers, integers, and their attendant operations. We\u2019ll also review prime factorizations, divisibility rules, and other basic topics pertaining to numbers. Numbers, Numbers Everywhere For some of you, it\u2019s been a long time since you\u2019ve darkened the doorway of a [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-206","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages\/206","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/comments?post=206"}],"version-history":[{"count":16,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages\/206\/revisions"}],"predecessor-version":[{"id":1447,"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/pages\/206\/revisions\/1447"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/elementary-education\/wp-json\/wp\/v2\/media?parent=206"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}