2007 AMC 8 Problems/Problem 18

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When you multiply $303$ by $505$, it's $153015$. The ones digit plus thousands digit is $5$ $+$ $3$ $=$ $8$. $30303$ $\times$ $50505$ $=$ $1530453015$. Note that the ones and thousands digits are, added together, $8$. (and so on...) So the answer is $\boxed{D}$ $(8)$.