Ruth walks at a constant speed of $5 \mathrm{~km} / \mathrm{h}$. How many minutes will it take her to walk $1.5 \mathrm{~km}$ ?
(A) 20
(B) 24
(C) 18
(D) 15
(E) 7.5
To walk $1.5 \mathrm{~km}$, Ruth takes $\frac{1.5 \mathrm{~km}}{5 \mathrm{~km} / \mathrm{h}}=0.3 \mathrm{~h}=18 \mathrm{~min}$.

Answer: (C)