<table  width="600" border="1" cellspacing="0" cellpadding="7">
    <tr class="tabla">
        <td >numero 1</td>
        <td >numero 2</td>
        <td>resultado</td>
    </tr>
    <tr class="tabla" onkeyup="myFunction(this)">
        <td id=""  contenteditable>11</td>
        <td id="" contenteditable>12</td>
        <td class="total"></td>
    </tr>

    <tr class="tabla" onkeyup="myFunction(this)">
        <td id=""  contenteditable></td>
        <td id=""  contenteditable></td>
        <td class="total"></td>
    </tr>

</table>


<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<script>
    function myFunction(o) {
/*        $('.tabla').each(function() {
            var _1 = $(this).find("td").eq(0).html();
            var _2 = $(this).find("td").eq(1).html();

            var _11=parseInt(_1);
            var _22=parseInt(_2);

            var total= _11 * _22 ;
            if( isNaN(total)){
                $('.total').html(0) ;
            }else{
                $('.total').html(total) ;
            }

        });*/
        var _tr = $(o);
        var _1 = _tr.find("td").eq(0).html();
        var _2 = _tr.find("td").eq(1).html();
        var _11=parseInt(_1);
        var _22=parseInt(_2);
        var total= _11 * _22 ;
        console.log(total);
        var _total = _tr.find("td").eq(2);
        if( isNaN(total)){
            _total.html(0) ;
        }else{
            _total.html(total) ;
        }

    }
</script>