Divs that won't add up

by Markus Mannheim

HTML

<body>
  <div class="outsideDiv">
    <div class="insideDiv" id="div1">width = 33%</div>
    <div class="insideDiv" id="div2">width = 33%</div>
    <div class="insideDiv" id="div3">width = 33%</div>
  </div>
</body>

CSS

body {
  margin: 0; padding: 0;
}

div {
  height: 100px;
}

.outsideDiv {
  width: 100%;
  color: white;
  background-color: black;
}

.insideDiv {
  display: inline-block;
  width: 33%;
}

#div1 {
  background-color: red;
}

#div2 {
  background-color: green;
}

#div3 {
  background-color: blue;
}