JSFiddle - React, Tailwind, and code Playground

HTML

<div></div><div></div><div></div>

CSS

body{
  margin: 0;
}

div{
  height: 200px;
  width: 33%; /* as @passatgt mentioned in the comment*/
  width: calc(100% / 3);
  display: inline-block;
}

div:first-of-type{background-color: red}
div:nth-of-type(2){background-color: blue}
div:nth-of-type(3){background-color: green}