You need to line up decimals for additional and subtraction. For multiplication, you don't need to line them up  in fact, it would serve no useful purpose.
http://wiki.answers.com/Q/How_line_up_multiply_dec...

No do not line the decimals.When multiplying numbers with
http://www.chacha.com/question/whenyoumultiplya...

multiply the numbers just like there was no decimals. When you get your answer, then you can add the decimal. Count the total number of decimal places in both factors and allow that
http://answers.yahoo.com/question/index?qid=200801...

Ignore the decimals for the moment. Multiply 9 x 7. Your answer is 63. Now count the number of digits to the right of the decimals in the original equation. That would be 2. Starting
http://uk.answers.yahoo.com/question/index?qid=201...
