Edit in JSFiddle

<div class="a_box">
    <div class="b_box"></div>
</div>
<br/>
<div class="d_box"></div>
<div class="c_box"></div>

.a_box {
    background:#000;
    width:200px;height: 200px;
} 
.d_box,
.b_box {
    background:red;
    width:100%;
    height: 100px;;
}

.c_box{
    background:#000;
    width:100%;
    height: 100px;;
}

.d_box,
.c_box {
    width:200px;
}