JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div class="div1">
        <img src="http://lorempixel.com/400/200" class="image" />
        <div class="div2">Needs to be 70% height of DIV1</div>
    </div>
</div>

CSS

.div1 {
    border: 2px solid red;
    height: auto;
}
.image {
    width: 50%;
}
.div2 {
    border: 3px solid blue;
    width: 40%;
    float: right;  
    position: absolute;
    right: 0;
    top: 0;
    bottom:50%;
}
.parent {
    overflow: hidden;
    position: relative;
    width: 100%;
}