e0279c51-72c9-4d0e-a87f-67db41181309.html

<h3>Cool Down (5 minutes)</h3>
<h4>Student Activity</h4>
<p><img src="https://k12.openstax.org/contents/raise/resources/ae8658c7e4af3aa7f945d258b183765ddd5efe97"></p>
<ol class="os-raise-noindent">
  <li> This graph represents one of the following descriptions. Which one? </li>
  <ol class="os-raise-noindent" type="a">
    <li> A phone loses \(\frac45\) of its value every year after purchase; the relationship between the number of years since purchasing the phone and the value of the phone. </li>
    <li> The number of stores a company has tripled approximately every 5 years; the relationship between the number of years and the number of stores. </li>
    <li> A camera loses \(\frac25\) of its value every year after purchase; the relationship between the number of years since purchasing the camera and the value of the camera. </li>
  </ol>
  <br>
  <p><strong>Answer:</strong> A camera loses \(\frac25\) of its value every year after purchase; the relationship between the number of years since purchasing the camera and the value of the camera.</p>
</ol>
<ol class="os-raise-noindent" start="2">
  <li> Explain how you know the graph represents the description you chose. <br>
    <strong>Answer:</strong> Compare your answer:
  </li>
</ol>
<ul>
  <ul>
    <ul>
      <li>The graph cannot represent Description A because the phone is retaining only \(\frac15\) of its value, which is less than half, and the vertical coordinate of the second point on the graph is more than half of the vertical intercept. </li>
      <li><span>If the camera loses \(\frac25\) of its value each year, then its value is \(\frac35\) that of the previous year. The vertical intercept seems to be 1,200, and \(\frac35\) of 1,200 is about 700, which is roughly the vertical coordinate of the second point.</span><br>
      </li>
    </ul>
  </ul>
</ul>
<h4>Response to Student Thinking</h4>
<h5> Points to Emphasize</h5>
<p>If a significant number of students choose option a, consider doing a think aloud in class to determine the rate of decay. Assign a practice problem from this lesson for students to consolidate their thinking. If students struggle to explain their reasoning, select a few examples of student work and discuss as a class what makes the reasoning clear or how the reasoning might be strengthened.</p>