DECIMAL arena
An example of how we can configure decimal.js to automatically round to the correct number of decimal places when JSON.stringify()-ed.
HTML
<script src="https://cdnjs.cloudflare.com/ajax/libs/decimal.js/10.0.0/decimal.min.js"></script>
<pre id="output"></pre>
JavaScript
let a = Decimal(71.2)
let b = Decimal(9)
let viva = Decimal(a).div(100)
let vida = Decimal(viva).mul(b).toFixed(2)
console.log(vida)
// console.log((a/100)*b)