onblur calculate the sum.

onblur calculate the sum.

i have a problem with total calculation on change input box
it only show the change box value, it don' t sum
in total input box.

can you please help me
here are  the code

<script> 
function calculat(id){

   var total= $("#bank_"+id).val();        // this will take the value of bank_1

     total+                                       // This do not work

   $("#total").val(total);                     // display in the total input box


   

}
</script>



<input type="text"  id="bank_1" onblur="calculat(1);" name="bank[1]" />
<input type="text"  id="bank_2" onblur="calculat(2);" name="bank[2]" />

<input type="text" name="total" id="total" />