<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>가로로 사각형들을 등분하기</title>
<style>
.box{border: 2px dotted black; padding: 10px;}
.top{background-color:coral; height: 200px; margin-bottom:10px;}
.bottom{background-color: cornflowerblue; height: 200px;}
</style>
</head>
<body>
<div class="box">
<div class="top"></div>
<div class="bottom"></div>
</div>
</body>
</html>