Binary multiplication help, need to multiply 2 8 bit numbers, but I cant get the required answer.

Question

So, i got this question for an assignment, it says "Compute the binary multiplication of 11110101 times 00001001 and verify that the result represents −99 (remember to only take the least significant 8 bits. Marks will be given for correct working and explanation."

I did the multiplication and got "100010011101", which isn't equal to -99. No matter how i do it, even using a calculator, i cant geet -99. What am i doing wrong. Thanks!

    Heres my working: 

----11110101 
----00001001 (multiplying) 
_____________ 
----11110101 
---00000000* 
--00000000** 
-11110101*** 
_____________ (adding) 
100010011101

Answer 1

I forgot to convert from unsigned binary to two's complement. So 10011101 is equal to -99 in two's complement.