Multiplying and Adding Numbers:

The example:

Price

Enter Quantity

Notice the result is "4.5", not "4.50", we'll create a function that will format the numbers correctly.

function format(value){
value*=100; value+="";
return value.substring(0,value.length-2)+"."+value.substring(value.length-2);
}

Price

Enter Quantity

More Maths.- a better formatting function