{"id":496,"date":"2017-10-28T22:24:07","date_gmt":"2017-10-28T22:24:07","guid":{"rendered":"http:\/\/pressbooks-dev.oer.hawaii.edu\/math111\/?post_type=chapter&p=496"},"modified":"2017-12-30T02:10:43","modified_gmt":"2017-12-30T02:10:43","slug":"addition-dots-and-boxes","status":"publish","type":"chapter","link":"https:\/\/pressbooks-dev.oer.hawaii.edu\/math111\/chapter\/addition-dots-and-boxes\/","title":{"raw":"Addition: Dots and Boxes","rendered":"Addition: Dots and Boxes"},"content":{"raw":"

[latexpage]<\/p>\r\n\r\n

Addition as combining<\/h1>\r\n

For now, we\u2019ll focus on the base-10 system. Here\u2019s how we think about the number 273 in that system:<\/p>\r\n

\"\"<\/p>\r\n

And here is the number 512:<\/p>\r\n

\"\"<\/p>\r\n\r\n

\r\n

Example: 273+512<\/h3>\r\n

We can add these in the natural way: just combine the piles of dots. Since they\u2019re already in place-value columns, we can combine dots from the two numbers that are in the same place-value box.<\/p>\r\n

\"\"<\/p>\r\n

We can count up the answer: there are 7 dots in the hundreds box, 8 dots in the tens box, and 5 dots in the ones box.<\/p>\r\n\\begin{align*}\r\n\\phantom{ + } 273 \\\\\r\n\\underline{+\u00a0 512} \\\\\r\n\\phantom{ + } 785\r\n\\end{align*}\r\n\r\nAnd saying out the long way we have:\r\n

    \r\n \t
  • Two hundreds plus five hundreds gives 7 hundreds.<\/li>\r\n \t
  • <\/i>Seven tens plus one ten gives 8 tens.<\/li>\r\n \t
  • <\/i>Three ones plus two ones gives 5 ones.<\/li>\r\n<\/ul>\r\n

    This gives the answer: 785.<\/p>\r\n[embed]https:\/\/www.youtube.com\/watch?v=h4FT4Lw8i7M[\/embed]\r\n\r\n<\/div>\r\n \r\n

    \r\n

    Example: 163+489<\/h3>\r\n

    Let\u2019s do another one. Consider 163+489.<\/p>\r\n

    \"\"<\/p>\r\n\\begin{align*}\r\n\\phantom{ +\\ } 1\\ \\ \\\u00a0 6\\ \\ \\ 3 \\\\\r\n\\underline{+\\\u00a0 4\\ \\ \\ 8\\ \\ \\ 9} \\\\\r\n\\phantom{ +\\ } 5\\, |\\, 14\\, |\\, 12\r\n\\end{align*}\r\n

    And this is absolutely correct:<\/p>\r\n\r\n

      \r\n \t
    • One hundred plus four hundreds is 5 hundreds.<\/li>\r\n \t
    • Six tens plus eight tens is 14 tens.<\/li>\r\n \t
    • Three ones plus nine ones is 12 ones.<\/li>\r\n<\/ul>\r\nThe answer is 5 | 14 | 12, which we might try to pronounce as \u201cfive hundred and fourteeny-tenty twelvety.\u201d The trouble with this answer is that most of the rest of the world wouldn\u2019t understand what we are talking about.\r\n\r\nSince this is a base 10 system, we can do some explosions.\r\n

      \"\"<\/p>\r\n

      \"\"<\/p>\r\n

      The answer is \u201csix hundred fifty two.\u201d Okay, the world can understand this one!<\/p>\r\n\\begin{align*}\r\n\\phantom{ +\\ } 1\\ \\ \\\u00a0 6\\ \\ \\ 3 \\phantom{\\ =\\ 652} \\\\\r\n\\underline{+\\\u00a0 4\\ \\ \\ 8\\ \\ \\ 9}\\phantom{\\ =\\ 652}\\\\\r\n\\phantom{ +\\ } 5\\, |\\, 14\\, |\\, 12\u00a0 =\\ 652\r\n\\end{align*}\r\n\r\n[embed]https:\/\/www.youtube.com\/watch?v=3LSl_c3exFU[\/embed]\r\n\r\n<\/div>\r\n \r\n

      \r\n

      Think \/ Pair \/ Share<\/h3>\r\n

      Solve the following exercises by thinking about the dots and boxes. (You can draw the pictures, or just imagine them.) Then translate the answer into something the rest of the world can understand.<\/p>\r\n\\begin{align*}\r\n\\phantom{ + } 148 &&\u00a0\\phantom{ + } 567\u00a0&&\u00a0\\phantom{ + } 310462872 \\\\\r\n\\underline{+\u00a0 323} &&\\underline{+\u00a0 271}&&\\underline{+\u00a0 389107123}\\\\\r\n\\phantom{ + 323}&&\u00a0\\phantom{ + 271}&&\u00a0\\phantom{ + 389107123}\\\\\r\n\\end{align*}\r\n\r\n \r\n\r\n<\/div>\r\n \r\n

      \r\n

      Problem 1<\/h3>\r\n

      Use the dots and boxes technique to solve these problems. Do not covert to base 10! Try to work directly in the base given. <\/i>It might help to actually draw the pictures.<\/p>\r\n\\begin{align*}\r\n\\phantom{ + } 20413_{\\text{five}} &&\u00a0\\phantom{ + } 4052_{\\text{nine}} &&\u00a0\\phantom{ + } 3323_{\\text{seven}} \\\\\r\n\\underline{+\u00a0 13244_{\\text{five}}} &&\\underline{+\u00a0 6288_{\\text{nine}}}&&\\underline{+\u00a0 3555_{\\text{seven}}}\\\\\r\n\\phantom{ + 20413_{\\text{five}}}&&\u00a0\\phantom{ +4052_{\\text{nine}}}&&\u00a0\\phantom{ + 3323_{\\text{seven}}}\\\\\r\n\\end{align*}\r\n\r\n<\/div>\r\n

      The Standard Algorithm for Addition<\/h1>\r\n

      Let\u2019s go back to the example 163+489. Some teachers don\u2019t like writing:<\/p>\r\n\\begin{align*}\r\n\\phantom{ + } 1\\ \\ \\\u00a0 6\\ \\ \\ 3 \\\\\r\n\\underline{+\u00a0 4\\ \\ \\ 8\\ \\ \\ 9} \\\\\r\n\\phantom{ + } 5\\, |\\, 14\\, |\\, 12 &= 652\r\n\\end{align*}\r\n

      They prefer to teach their students to start with the 3 and 9 at the end and sum those to get 12. This is of course correct \u2014 we got 12 as well.<\/p>\r\n

      \"\"<\/p>\r\n

      But they don\u2019t want students to write or think \u201ctwelvety,\u201d so they have their students write something like this:<\/p>\r\n\\begin{align*}\r\n\\phantom{+ 1}1\\phantom{3}\\\\\r\n\\phantom{ + } 163\\\\\r\n\\underline{+\u00a0 489}\\\\\r\n\\phantom{ + 48}2\\\\\r\n\\end{align*}\r\n

      This can seem completely mysterious. What\u2019s really going on? They are exploding ten dots, of course!<\/p>\r\n

      \"\"<\/p>\r\n

      Now we carry on with the problem and add the tens. Students are taught to write:<\/p>\r\n\\begin{align*}\r\n\\phantom{+ }1\\phantom{63}\\\\\r\n\\phantom{ + } 163\\\\\r\n\\underline{+\u00a0 489}\\\\\r\n\\phantom{ + 4}52\\\\\r\n\\end{align*}\r\n

      But what this means is better shown in this next picture.\u00a0 Notice the \"exploded\" (or regrouped) dot at the very top, which is added to the tens box in the answer.<\/p>\r\n

      \"\"<\/p>\r\n

      And now we finish the problem by combining the dots in the hundreds boxes:<\/p>\r\n

      \"\"<\/p>\r\n\\begin{align*}\r\n\\phantom{+ }1\\phantom{63}\\\\\r\n\\phantom{ + } 163\\\\\r\n\\underline{+\u00a0 489}\\\\\r\n\\phantom{ + }652\\\\\r\n\\end{align*}\r\n

      In the standard algorithm, we work from right to left, doing the \u201cexplosions\u201d as we go along. This means that we start adding at the ones place and work towards the left-most place value, \u201ccarrying\u201d digits that come from the explosions. (This is really not carrying; a better term for it is regrouping<\/i>. Ten ones become one ten. Ten tens become one hundred. And so on.)<\/p>\r\n

      In the dots and boxes method, we add in any direction or order we like and then we do the explosions at the end.<\/p>\r\n\r\n

        \r\n \t
      • <\/i>Why do we like the standard algorithm?<\/b> Because it is efficient.<\/li>\r\n \t
      • <\/i>Why do we like the dots and boxes method?<\/b> Because it is easy to understand.<\/li>\r\n<\/ul>\r\n ","rendered":"

        \n

        Addition as combining<\/h1>\n

        For now, we\u2019ll focus on the base-10 system. Here\u2019s how we think about the number 273 in that system:<\/p>\n

        \"\"<\/p>\n

        And here is the number 512:<\/p>\n

        \"\"<\/p>\n

        \n

        Example: 273+512<\/h3>\n

        We can add these in the natural way: just combine the piles of dots. Since they\u2019re already in place-value columns, we can combine dots from the two numbers that are in the same place-value box.<\/p>\n

        \"\"<\/p>\n

        We can count up the answer: there are 7 dots in the hundreds box, 8 dots in the tens box, and 5 dots in the ones box.<\/p>\n

          <\/span>   <\/span>\"\begin{align*}<\/p>\n

        And saying out the long way we have:<\/p>\n

          \n
        • Two hundreds plus five hundreds gives 7 hundreds.<\/li>\n
        • <\/i>Seven tens plus one ten gives 8 tens.<\/li>\n
        • <\/i>Three ones plus two ones gives 5 ones.<\/li>\n<\/ul>\n

          This gives the answer: 785.<\/p>\n