float后，DIV没有被撑大的处理办法

<div style="width:200px;border:1px solid red;">
    <div style="float:left;width:80px;height:80px;border:1px solid blue;">TEST DIV</div>
    <div style="float:left;width:80px;height:80px;border:1px solid blue;">TEST DIV</div>
    <div style="float:left;width:80px;height:80px;border:1px solid blue;">TEST DIV</div>
    <div style="float:left;width:80px;height:80px;border:1px solid blue;">TEST DIV</div>
    <div style="float:left;width:80px;height:80px;border:1px solid blue;">TEST DIV</div>
    <div style="clear:both;"></div>
</div>

显示的结果如下：