title: change selects value onchange of another select
body: <p>i start learning jquery few days ago, and i like it very much. but now i have a problem, that can't solve alone.</p>
  
  <p>i have two selects</p>
  
  <pre><code>&lt;select id="select1"&gt;
    &lt;option value="1"&gt;1day&lt;/option&gt;
    &lt;option value="2"&gt;2day&lt;/option&gt;
    &lt;option value="3"&gt;3day&lt;/option&gt;
  &lt;/select&gt;
  
  &lt;select id="select2"&gt;
    &lt;option value="1"&gt;1day&lt;/option&gt;
    &lt;option value="2"&gt;2day&lt;/option&gt;
    &lt;option value="3"&gt;3day&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>i need to set <code>#select2</code> the same value with <code>#select1</code>, when <code>#select1</code> changes</p>
  
  <p>i've red some questions about select tag <a href="https://stackoverflow.com/questions/149573/check-if-option-is-selected-with-jquery-if-not-select-a-default">here</a>, but i need to set "selected" attribute to that option, which have the same value. how can i do it?</p>
  
  <p>Thanks</p>