How can you set the height of an outer div to always be equal to a particular inner div?

Question

I have an outer div which contains three inner divs.

I want the left-most inner div to always determine the height of the outer div. If the other in

Answer 1

different ways. two examples:

.outer_div {
  position: relative;
  overflow: hidden;
  max-width: 300px;
  margin: 0 auto;
}
.inner_div {
  width: 33.33%;
}
.inner_div_1 {
  float: left;
  background: khaki;
}
.inner_div_2,
.inner_div_3 {
  background: darkkhaki;
  position: absolute;
  top: 0;
  height: 100%;
  overflow-y: auto;
}
.inner_div_2 {
  left: 33.33%;
}
.inner_div_3 {
  left: 66.66%;
}

  

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.outer_div {
  display: flex;
  flex-direction: row;
  max-width: 300px;
  margin: 0 auto;
  background : gray;
}
.inner_div {
  width: 33.33%;
}
.inner_div > div {
  position: relative;
  height: 100%;
}
.inner_div_1 span {
  background: khaki;
}
.inner_div_2 span,
.inner_div_3 span {
  background: darkkhaki;
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  overflow-y: auto;
  overflow-x: hidden;
}

  

    
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        Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.