JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <input  name="r"  class="rate" type="text" maxlength="255" size="5" value=""/> 
    <input  name="p" class="pack" type="text" maxlength="255" size="5" value=""/> 
    <input  name="b" class="bag" type="text" maxlength="255" size="5" value=""/> 
    <input  name="w" class="weight" type="text" maxlength="255" size="5" value=""/> 
    <span  class="amount"></span> 
</div>
<div>
    <input  name="r"  class="rate" type="text" maxlength="255" size="5" value=""/> 
    <input  name="p" class="pack" type="text" maxlength="255" size="5" value=""/> 
    <input  name="b" class="bag" type="text" maxlength="255" size="5" value=""/> 
    <input  name="w" class="weight" type="text" maxlength="255" size="5" value=""/>
    <span class="amount"></span> 
</div>
<div>
    <input  name="r"  class="rate" type="text" maxlength="255" size="5" value=""/> 
    <input  name="p" class="pack" type="text" maxlength="255" size="5" value=""/> 
    <input  name="b" class="bag" type="text" maxlength="255" size="5" value=""/> 
    <input  name="w" class="weight" type="text" maxlength="255" size="5" value=""/>
    <span class="amount"></span> 
</div>
<div class="total_amount">total</div>

JavaScript

//any time the amount changes
$(document).ready(function() {
    $('input[name=r],input[name=p]').change(function(e) {
        var total = 0;
        var $row = $(this).parent();
        var rate = $row.find('input[name=r]').val();
        var pack = $row.find('input[name=p]').val();
        total = parseFloat(rate * pack)*100;
        //update the row total
        $row.find('.amount').text(total);

        var total_amount = 0;
        $('.amount').each(function() {
            //Get the value
            var am= $(this).text();
            console.log(am);
            //if it's a number add it to the total
            if (IsNumeric(am)) {
                total_amount += parseFloat(am, 10);
            }
        });
        $('.total_amount').text(total_amount);
    });
});

//isNumeric function Stolen from: 
//http://stackoverflow.com/questions/18082/validate-numbers-in-javascript-isnumeric

function IsNumeric(input) {
    return (input - 0) == input && input.length > 0;
}