On a trip to the beach, Anh traveled 50 miles on the highway and 10 miles on a coastal access road. He drove three times as fast on the highway as on the coastal road. If Anh spent 30 minutes driving on the coastal road, how many minutes did his entire trip take?
$\textbf{(A) }50\qquad\textbf{(B) }70\qquad\textbf{(C) }80\qquad\textbf{(D) }90\qquad \textbf{(E) }100$
Since Anh spends half an hour to drive 10 miles on the coastal road, his speed is $r=\frac dt=\frac{10}{0.5}=20$ mph. His speed on the highway then is $60$ mph. He drives $50$ miles, so he drives for $\frac{5}{6}$ hours, which is equal to $50$ minutes (Note that $60$ miles per hour is the same as $1$ mile per minute). The total amount of minutes spent on his trip is $30+50\implies \boxed{\textbf{(C) }80}$.