Sumar values de multiples select usando jquery

<select name='anch1'>
 <option value='10'>10 ++</option>
 <option value='20'>20 ++</option>
 <option value='30'>30 ++</option>
 <option value='40'>40 ++</option>
 <option value='50'>50 ++</option>
</select>





<select name='anch2'>
 <option value='10'>10 ++</option>
 <option value='20'>20 ++</option>
 <option value='30'>30 ++</option>
 <option value='40'>40 ++</option>
 <option value='50'>50 ++</option>
</select>

<select name='anch3'>
 <option value='10'>10 ++</option>
 <option value='20'>20 ++</option>
 <option value='30'>30 ++</option>
 <option value='40'>40 ++</option>
 <option value='50'>50 ++</option>
</select>

<div id='sum'>SUM OF SELECTED OPTIONS</div>

<script>

$('select').change(function(){
    var sum = 0;
    $('select :selected').each(function() {
        sum += Number($(this).val());
    });
     $("#sum").html(sum);
});

</script>