[jQuery] element selection problem

[bob]

What is the best way to select
class="explanation"?
I have available array
var idArray = ['yyyy', 'state','gender'];

I tried this
jQuery('#'+idArray[i]+'Sector div.ex');
and it did not work.

Note: I cannot use id inside of <div class="explanation"></div>

<div id="yyyySector">
        <input type="text" name="yyyy" id="yyyy" value="" size="4"
maxlength="4">
        <div class="explanation"></div>
</div>

<div id="stateSector">
        <select id="state" name="state">
                <option value='AL'>Alabama</option>
                <option value='AK'>Alaska</option>
        </select>
        <div class="explanation"></div>
</div>

<div id="genderSector">
        <input type="radio" name="f" id="f" value="1" />Female
        <input type="radio" name="m" id="m" value="2" />Male
        <div class="explanation"></div>
</div>