Div expand to fit

HTML

<div id="wrap">
    <div id="one"></div>
    <div id="two"></div>
</div>

CSS

div#wrap {
    width: 100%;
    height: 200px;
    background: aqua;
    padding: 10px;
}
div#one {    
    width: 25%;
    height: 100px;
    background: red;
    float: left;
}
div#two {
    margin-left: 15%;
    height: 100px;
    background: black;
}