I need to find the rate of words per hour, which is the ratio of words to hours. I can use division to find this ratio: $40,\!000 \div 80$. I can use long division or a calculator to find the quotient. I get $500$ as the quotient, which means the author wrote $500$ words per hour on average. 
A particular novel contains $40,\!000$ words. If the author completed the novel in $80$ hours, on average how many words per hour did she write?