Edit in JSFiddle

<div class="BFC">
    <p>
    hello world
    </p>
</div>
 
<p>
    hello world
</p>
<p>
    hello world
</p>

.BFC{
    overflow:hidden;
}
p{
    color:black;
    background:#F00;
    line-height:100px;
    width:200px;
    text-align:center;
    margin:50px;
}