A local library manager randomly surveys 80 patrons about the type of book they borrow when they visit. The manager finds that 3 patrons from the survey borrow novels. If the local library has 345 patrons, approximately how many of them borrow books when they visit? Round the answer to the nearest whole number.
Let $n$ be the number of patrons who borrow books when they visit. We set up a proportion to find $n$. $\frac{3}{80}\approx \frac{n}{345}.$ We cross multiply to get $80n\approx 3\cdot 345$, which gives $n\approx \frac{3\cdot 345}{80} \approx 12.9.$ Rounding to the nearest whole number, $n=\boxed{13}$.
