<div class="flex">
  <div class="item">flex-grow: 1;</div>
  <div class="item">flex-grow: 1;</div>
  <div class="item">flex-grow: 1;</div>
  <div class="item">flex-grow: 1;</div>
  <div class="item">flex-grow: 1;</div>
</div>
.flex {
  display: flex;
  flex-wrap: wrap;
  
  > * {
    display: flex;
    align-items: center;
    justify-content: center;
    box-sizing: border-box;
    height: 240px;
    border: 4px solid #888;
    font-weight: 700;
    font-family: arial, sans-serif;
  }
}

.item {
  flex: 1 1 240px;
  background: #faa;
}

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