JSFiddle - React, Tailwind, and code Playground

HTML

<body>
  <div class="grid">
    <div class="block"></div>
    <div class="block"></div>
    <div class="block"></div>
    <div class="block"></div>
    <div class="block"></div>
  </div>
</body>

CSS

.grid {
    display: flex;
    flex-wrap:wrap;
}

.grid > div {
    background: red;
    height: 100px;
    margin: 10px;
    flex-grow: 1;    
   width: calc(100% * (1/3) - 10px - 10px);
}