<div class="box">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item"><code>grid-column-end: 4;</code></div>
  <div class="item">5</div>
  <div class="item">6</div>
  <div class="item">7</div>
  <div class="item">8</div>
  <div class="item">9</div>
  <div class="item">10</div>
</div>
.box {
  display: grid;
  grid-template-columns: 1fr 1fr 2fr;
  grid-gap: 2px;
}

.box .item {
  background-color: tomato;
  color: white;
  font-size: 1.4em;
  font-family: monospace;
  padding: 16px;
}

.box .item:nth-child(4) {
  grid-column-end: 4;
  background: gold;
}

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