JSFiddle - React, Tailwind, and code Playground

HTML

<div id="p_scents">
    <p>
        <input type="text" id="p_scnt" class="grade" size="20" name="p_scnt" value="" placeholder="Grade" />
        <input type="text" id="p_scnt" class="units" size="20" name="p_scnt" value="" placeholder="Units" />
    </p>
</div>
<h2><a href="#" id="addScnt">Add Another Input Box</a></h2>

<input id="addAll" type="button" value="Sum all Textboxes" /><br />
<p id="para" /></p>

JavaScript

$(function() {
        var scntDiv = $('#p_scents');
        var i = $('#p_scents p').size() + 1;
        
        $('#addScnt').live('click', function() {
                $('<p><input type="text" id="p_scnt" class="grade" size="20" name="p_scnt_' + i +'" value="" placeholder="Grade" />\n<input type="text" id="p_scnt" class="units" size="20" name="p_scnt_' + i +'" value="" placeholder="Units" /> <a href="#" id="remScnt">Remove</a></p>').appendTo(scntDiv);
                i++;
                return false;
        });
        
        $('#remScnt').live('click', function() { 
                if( i > 2 ) {
                        $(this).parents('p').remove();
                        i--;
                }
                return false;
        });
	});


        $(function() {
            $("#addAll").click(function() {
                var grade = 0;
                var units = 0;
                
                var grades = $(".grade");
                var units = $(".units");
                var total = 0;
                var unitsTotal = 0;
                
                for (var i = 0; i < grades.length; i++)
                {
                    total += Number($(grades).eq(i).val()) * Number($(units).eq(i).val());
                    unitsTotal += Number($(units).eq(i).val());
                }
                
                var average = total / unitsTotal;
                
                $("#para").text("Average is : " + average);
            });
        });