You have been multiplying all of each successive product by 8. You are supposed to multiply only the fractional part (the part to the right of the decimal point) by 8 each time. Here is what you did:
You then used the integral parts of your products as your answer (and forgot to use the 0 in 40). You must multiply only the fractional part of each successive product. In this way the integral parts of each successive product will always be a single integer (which may be 0).