openfreebooks-bookgenerator/content/math/basic-math-notation/core.html

<div class="book-prose">
  <p>
    In the last chapter you met <strong>number sentences</strong> — short lines that use digits and
    special marks, like <strong>3 + 4 = 7</strong>. This chapter is a guide to those marks: what each
    one is called, how to say it out loud, and what it tells you to do. You do not need to be fast at
    arithmetic yet; you only need to <strong>read</strong> the symbols like words on a sign.
  </p>

  <h2 id="history" class="book-prose__heading">History</h2>
  <p>
    People counted with fingers and words long before they agreed on one way to write math. Ancient
    Egyptians and Babylonians used pictures and marks for amounts. Over centuries, different
    countries used different symbols for the same ideas.
  </p>

  <figure class="book-figure">
    <img
      class="book-figure__img"
      src="/chapters/math/basic-math-notation/basic-math-notation-history.png"
      alt="Cartoon timeline: counting long ago, Egyptian and Babylonian marks, different symbols around the world, then equals, plus and minus, times and divide, and brackets for grouping"
      width="960"
      height="640"
      loading="lazy"
      decoding="async"
    />
    <figcaption class="book-figure__caption">
      From finger counting and ancient marks to short symbols on one line: how +, −, ×, ÷, =, and ( )
      became the signs you read today.
    </figcaption>
  </figure>

  <p>
    The <strong>equals sign</strong> (=) was popularised in the 1500s by Welsh mathematician
    <strong>Robert Recorde</strong>. He chose two lines because “no two things can be more equal” than
    parallel lines — a way to show both sides match.
  </p>
  <p>
    The <strong>plus</strong> and <strong>minus</strong> signs (+ and −) became common in Europe
    around the same era, replacing longer Latin words. The <strong>times</strong> sign (×) and
    <strong>division</strong> sign (÷) appeared later, when printing books needed short, clear marks
    that fit on one line.
  </p>
  <p>
    Brackets grew important when formulas got longer — mathematicians needed a visible rule for
    “which part first,” just like you do in <strong>(2 + 3) + 4</strong>.
  </p>

  <h2 id="digits-and-words" class="book-prose__heading">Digits, words, and spaces</h2>
  <p>
    The symbols <strong>0</strong> through <strong>9</strong> are called <strong>digits</strong>. Each
    digit stands for a counting amount (zero through nine). When you write a bigger number, you put
    digits side by side with no gap: <strong>47</strong> means four tens and seven ones.
  </p>
  <p>
    A full line of math often mixes <strong>words</strong> (in your head or in a story) with
    <strong>symbols</strong> (on paper). “Three plus four equals seven” is the same idea as
    <strong>3 + 4 = 7</strong>.
  </p>

  <div class="book-table-wrap">
    <table class="book-table notation-symbol-table">
      <thead>
        <tr>
          <th scope="col">Symbol</th>
          <th scope="col">Name</th>
          <th scope="col">Say it like this</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <td class="notation-symbol-table__glyph">0–9</td>
          <td>digits</td>
          <td>“zero”, “one”, … “nine”</td>
        </tr>
        <tr>
          <td class="notation-symbol-table__glyph">(space)</td>
          <td>space between parts</td>
          <td>pause between numbers and signs so the line is easy to read</td>
        </tr>
      </tbody>
    </table>
  </div>

  <h2 id="plus" class="book-prose__heading">Plus (+)</h2>
  <p>
    The <strong>plus sign</strong> looks like a small cross: <strong>+</strong>. It means
    <strong>put together</strong> or <strong>add</strong>.
  </p>
  <p>
    Read <strong>3 + 4 = 7</strong> as: “three <em>plus</em> four <em>equals</em> seven.” You are
    joining two groups into one total.
  </p>

  <div class="book-callout" role="note">
    <p class="book-callout__label">Remember</p>
    <p>The plus sign is not the letter “t”. It sits between the numbers you are combining.</p>
  </div>

  <h2 id="minus" class="book-prose__heading">Minus (−)</h2>
  <p>
    The <strong>minus sign</strong> is a short horizontal line: <strong>−</strong> (sometimes written
    as a hyphen <strong>-</strong> on a keyboard). It means <strong>take away</strong> or
    <strong>subtract</strong>.
  </p>
  <p>
    Read <strong>7 − 3 = 4</strong> as: “seven <em>minus</em> three <em>equals</em> four.” Start with
    seven things, remove three, and count what is left.
  </p>

  <div class="book-callout" role="note">
    <p class="book-callout__label">Minus or hyphen?</p>
    <p>
      In a <strong>number sentence</strong>, the short line between numbers is a <strong>minus
      sign</strong>. In ordinary writing, the same shape can join words (like “well-known”) — that
      is a <strong>hyphen</strong>, not “take away.” Look at what is on each side: digits mean minus.
    </p>
  </div>

  <h2 id="times" class="book-prose__heading">Times (×)</h2>
  <p>
    The <strong>times sign</strong> looks like a tilted cross or letter x: <strong>×</strong>. It
    means <strong>multiply</strong> — many <em>equal</em> groups.
  </p>
  <p>
    Our main example is <strong>three groups of four makes twelve</strong>. You can spell that same
    fact in several ways on paper:
  </p>
  <ul>
    <li>Plain with a cross: <strong>3 × 4 = 12</strong></li>
    <li>Plain with a middle dot: <strong>3 · 4 = 12</strong></li>
    <li>Plain like a keyboard: <strong>3 * 4 = 12</strong></li>
    <li>Plain as repeated adding: <strong>4 + 4 + 4 = 12</strong> (three fours)</li>
    <li>Typeset math: \(3 \times 4 = 12\) and \(3 \cdot 4 = 12\) — same story, neater symbols.</li>
  </ul>
  <p>
    Read any of the lines above as: “three <em>times</em> four <em>equals</em> twelve,” or “three
    groups of four.”
  </p>

  <h2 id="divide" class="book-prose__heading">Divide (÷)</h2>
  <p>
    The <strong>division sign</strong> is a dot with a line: <strong>÷</strong>. It means
    <strong>split into equal groups</strong> or <strong>share fairly</strong>.
  </p>
  <p>
    Take <strong>twelve shared into four equal piles; each pile has three</strong>. Again, the same
    fact can look different on the page:
  </p>
  <ul>
    <li>Plain with obelus: <strong>12 ÷ 4 = 3</strong></li>
    <li>Plain with a slash (like a fraction lying down): <strong>12/4 = 3</strong></li>
    <li>Typeset with a fraction bar: \(\dfrac{12}{4} = 3\) — top number “twelve,” bottom “four,” whole value “three.”</li>
  </ul>
  <p>
    Read <strong>12 ÷ 4 = 3</strong> or <strong>12/4 = 3</strong> as: “twelve <em>divided by</em> four
    <em>equals</em> three.” Twelve dots shared into four equal piles give three in each pile.
  </p>
  <p>
    A <strong>slash</strong> between two numbers is a quick way to write division or a fraction in one
    line: <strong>1/2</strong> is “one half,” and <strong>12/4</strong> is the same sharing story as
    twelve divided by four. In typeset math the numbers can sit one above the other:
    \(\tfrac{1}{2}\) (one half) and \(\dfrac{12}{4} = 3\) (twelve over four equals three).
  </p>

  <h2 id="equals" class="book-prose__heading">Equals (=)</h2>
  <p>
    The <strong>equals sign</strong> is two parallel lines: <strong>=</strong>. It means
    <strong>is the same amount as</strong> on both sides.
  </p>
  <p>
    Read a full sentence from left to right. In <strong>5 + 2 = 7</strong>, the left side (five plus
    two) has the same total as the right side (seven). The equals sign is the bridge between them.
  </p>

  <div class="book-callout" role="note">
    <p class="book-callout__label">One sentence</p>
    <p>
      Treat the whole line as one idea: “five plus two equals seven.” Do not stop reading at the plus
      sign — finish at the number after the equals sign.
    </p>
  </div>

  <h2 id="brackets" class="book-prose__heading">Brackets ( )</h2>
  <p>
    <strong>Round brackets</strong> — also called <strong>parentheses</strong> — wrap part of a
    sentence: <strong>(</strong> and <strong>)</strong>. They mean: <strong>do this group
    first</strong>, then use the result with the rest of the line.
  </p>
  <p>
    In <strong>(2 + 3) + 4</strong>, add two and three inside the brackets to get five, then add four
    to get nine. Without brackets, <strong>2 + 3 + 4</strong> still totals nine, but brackets help
    when the order would be unclear.
  </p>

  <h2 id="quick-reference" class="book-prose__heading">Quick reference: the main four operations</h2>
  <div class="book-table-wrap">
    <table class="book-table notation-symbol-table">
      <thead>
        <tr>
          <th scope="col">Symbol</th>
          <th scope="col">Name</th>
          <th scope="col">Meaning</th>
          <th scope="col">Example</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <td class="notation-symbol-table__glyph">+</td>
          <td>plus</td>
          <td>put together</td>
          <td>3 + 4 = 7</td>
        </tr>
        <tr>
          <td class="notation-symbol-table__glyph">−</td>
          <td>minus</td>
          <td>take away</td>
          <td>7 − 3 = 4</td>
        </tr>
        <tr>
          <td class="notation-symbol-table__glyph">×</td>
          <td>times</td>
          <td>equal groups</td>
          <td>3 × 4 = 12</td>
        </tr>
        <tr>
          <td class="notation-symbol-table__glyph">÷</td>
          <td>divided by</td>
          <td>fair shares</td>
          <td>12 ÷ 4 = 3</td>
        </tr>
        <tr>
          <td class="notation-symbol-table__glyph">=</td>
          <td>equals</td>
          <td>same amount both sides</td>
          <td>5 + 2 = 7</td>
        </tr>
        <tr>
          <td class="notation-symbol-table__glyph">( )</td>
          <td>brackets</td>
          <td>this part first</td>
          <td>(2 + 3) + 4 = 9</td>
        </tr>
      </tbody>
    </table>
  </div>

  <h2 id="compare" class="book-prose__heading">Less than and greater than (&lt; &gt;)</h2>
  <p>
    Sometimes we compare two amounts without adding or subtracting. Think of
    <strong>&lt;</strong> and <strong>&gt;</strong> as a hungry mouth: the open side points at the
    <strong>bigger</strong> number — it “wants” the larger pile.
  </p>
  <ul>
    <li><strong>&lt;</strong> means <strong>less than</strong> — the mouth opens toward the bigger number on the right.</li>
    <li><strong>&gt;</strong> means <strong>greater than</strong> — the mouth opens toward the bigger number on the left.</li>
  </ul>

  <h3 id="compare-examples" class="book-prose__heading">More examples</h3>
  <p>Read each line like a short sentence. The symbol tells you which side is bigger:</p>
  <ul>
    <li><strong>3 &lt; 7</strong> — “three is less than seven.”</li>
    <li><strong>9 &gt; 5</strong> — “nine is greater than five.”</li>
    <li><strong>2 &lt; 6</strong> — “two is less than six.”</li>
    <li><strong>8 &gt; 3</strong> — “eight is greater than three.”</li>
    <li><strong>5 &lt; 5</strong> is <strong>not</strong> true — five is the same as five, not less.</li>
    <li><strong>4 &lt; 4</strong> is also false — use <strong>=</strong> when both sides match.</li>
  </ul>
  <p>
    The same idea works either way: <strong>7 &gt; 4</strong> and <strong>4 &lt; 7</strong> both say
    that seven is the bigger amount.
  </p>

  <h3 id="compare-chain" class="book-prose__heading">A longer compare line</h3>
  <p>
    You can chain comparisons when several numbers line up from <strong>biggest to smallest</strong>
    (or the other way around). Read it in order, one piece at a time:
  </p>
  <p>
    <strong>9 &gt; 7 &gt; 4 &gt; 1</strong> — “nine is greater than seven, greater than four, greater
    than one.” Each number is bigger than the one to its right.
  </p>
  <p>
    In words: nine is greater than seven; seven is greater than four; four is greater than one. The
    whole chain means <strong>nine wins</strong> and <strong>one is smallest</strong>.
  </p>
  <figure class="notation-compare-chain" role="group" aria-label="Nine dots, then seven, then four, then one; each group has fewer dots than the group before">
    <ol class="notation-compare-chain__ladder">
      <li class="notation-compare-chain__step">
        <span class="notation-compare-chain__digit">9</span>
        <span class="notation-dots notation-dots--chain" role="img" aria-hidden="true">
          <span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span>
        </span>
      </li>
      <li class="notation-compare-chain__sign" aria-hidden="true">&gt;</li>
      <li class="notation-compare-chain__step">
        <span class="notation-compare-chain__digit">7</span>
        <span class="notation-dots notation-dots--chain" role="img" aria-hidden="true">
          <span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span>
        </span>
      </li>
      <li class="notation-compare-chain__sign" aria-hidden="true">&gt;</li>
      <li class="notation-compare-chain__step">
        <span class="notation-compare-chain__digit">4</span>
        <span class="notation-dots notation-dots--chain" role="img" aria-hidden="true">
          <span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span>
        </span>
      </li>
      <li class="notation-compare-chain__sign" aria-hidden="true">&gt;</li>
      <li class="notation-compare-chain__step">
        <span class="notation-compare-chain__digit">1</span>
        <span class="notation-dots notation-dots--chain" role="img" aria-hidden="true">
          <span class="notation-dots__dot"></span>
        </span>
      </li>
    </ol>
    <figcaption class="notation-compare-chain__caption">
      Nine dots &gt; seven dots &gt; four dots &gt; one dot — the pictures shrink the same way the
      numbers do.
    </figcaption>
  </figure>
  <p>
    You can flip the story for “smallest first”: <strong>1 &lt; 4 &lt; 7 &lt; 9</strong> — “one is
    less than four, less than seven, less than nine.” Same order, different mouths.
  </p>

  <div class="book-callout" role="note">
    <p class="book-callout__label">Or the same amount</p>
    <p>
      You may also see <strong>≤</strong> (less than or equal) and <strong>≥</strong> (greater than or
      equal). The extra line means “or the same amount,” like <strong>5 ≤ 5</strong>.
    </p>
  </div>

  <h2 id="comma-decimal" class="book-prose__heading">Comma and decimal point</h2>
  <p>
    In big numbers like <strong>1,000</strong>, a <strong>comma</strong> groups digits in threes so
    the number is easier to read — one thousand, not “one zero zero zero” as separate ideas.
  </p>
  <p>
    A <strong>decimal point</strong> <strong>.</strong> is a tiny dot that acts like a
    <strong>fence</strong> in a number. Everything on the <strong>left</strong> counts whole things
    you can line up (1, 2, 3, …). Everything on the <strong>right</strong> tells a
    <strong>piece</strong> of one more thing — not another full thing.
  </p>
  <p>
    Take <strong>3.5</strong>. Read it as <strong>“three and a half”</strong>: three full ones, plus
    half of the next one. The digit <strong>5</strong> after the point does <em>not</em> mean “five
    more marbles” — it names how much of the <em>next</em> whole you have filled in.
  </p>
  <figure class="notation-decimal-demo" role="group" aria-label="Three point five shown as three whole dots and half of a fourth">
    <p class="notation-decimal-demo__label">
      <span class="notation-decimal-demo__whole">3</span><span class="notation-decimal-demo__point" aria-hidden="true">.</span><span class="notation-decimal-demo__fraction">5</span>
      <span class="notation-decimal-demo__words">three and a half</span>
    </p>
    <div class="notation-decimal-demo__picture">
      <div class="notation-decimal-demo__wholes" aria-hidden="true">
        <span class="notation-dots notation-dots--decimal" role="presentation">
          <span class="notation-dots__dot"></span><span class="notation-dots__dot"></span><span class="notation-dots__dot"></span>
        </span>
        <span class="notation-decimal-demo__fence" aria-hidden="true">·</span>
        <span class="notation-decimal-demo__half" role="presentation">
          <span class="notation-decimal-demo__half-bar">
            <span class="notation-decimal-demo__half-on"></span>
            <span class="notation-decimal-demo__half-off"></span>
          </span>
        </span>
      </div>
    </div>
    <figcaption class="notation-decimal-demo__caption">
      Left of the fence: three whole dots. Right of the fence: half of the next dot filled in — that
      is what <strong>3.5</strong> means.
    </figcaption>
  </figure>
  <p>
    In a shop, <strong>3.50</strong> often means three dollars and fifty cents: dollars are whole
    steps on the left, cents are small pieces on the right. You will learn more about decimals later;
    for now, remember the point splits “how many wholes” from “how much of the next one.”
  </p>

  <h2 id="fractions" class="book-prose__heading">Fractions (½ and 1/2)</h2>
  <p>
    A <strong>fraction</strong> names <strong>part of a whole</strong> split into equal pieces. You
    might see a single character like <strong>½</strong>, or plain text with a slash
    <strong>1/2</strong>, or the same value written tall in math as \(\tfrac{1}{2}\) — all mean
    <strong>one part out of two equal parts</strong>.
  </p>
  <figure class="notation-fraction-demo" role="group" aria-label="One half: one shaded part of two equal parts">
    <span class="notation-fraction-demo__bar" aria-hidden="true">
      <span class="notation-fraction-demo__part notation-fraction-demo__part--on"></span>
      <span class="notation-fraction-demo__part"></span>
    </span>
    <figcaption class="notation-fraction-demo__caption">One half shaded — ½ of the bar</figcaption>
  </figure>

  <h2 id="percent" class="book-prose__heading">Percent (%)</h2>
  <p>
    The <strong>percent sign</strong> <strong>%</strong> means <strong>out of one hundred</strong>.
    <strong>50%</strong> means fifty out of every hundred — half of the whole. If a test has 100
    points and you score 80, you might say you got <strong>80%</strong>.
  </p>

  <h2 id="ellipsis-approx" class="book-prose__heading">And so on (…) and about (≈)</h2>
  <p>
    Three dots in a row <strong>…</strong> (an <strong>ellipsis</strong>) mean the pattern keeps
    going the same way: <strong>2, 4, 6, 8, …</strong> — two, four, six, eight, and so on.
  </p>
  <p>
    The sign <strong>≈</strong> means <strong>approximately</strong> or <strong>about</strong> — close
    but not exact. <strong>10 ÷ 3 ≈ 3</strong> is a rough answer; the exact value is a bit more than
    three.
  </p>

  <h2 id="more-signs-later" class="book-prose__heading">Signs you will meet later</h2>
  <p>
    As you grow, books will add more symbols: a <strong>colon</strong> for ratios, small numbers
    above the line for powers, and pairs of letters in graphs. You do not need them yet; this chapter
    is enough to read everyday number sentences.
  </p>

  <h2 id="try-it-yourself" class="book-prose__heading">Try it yourself</h2>
  <p>
    Say each line out loud before you calculate. Cover the answer with your hand, then check:
  </p>
  <ul>
    <li><strong>6 + 1 = 7</strong> — “six plus one equals seven”</li>
    <li><strong>10 − 4 = 6</strong> — “ten minus four equals six”</li>
    <li><strong>2 × 5 = 10</strong> — “two times five equals ten”</li>
    <li><strong>8 ÷ 2 = 4</strong> — “eight divided by two equals four”</li>
    <li><strong>(1 + 2) × 3 = 9</strong> — brackets first: one plus two is three; three times three is nine</li>
  </ul>
</div>