Lakshmi is travelling at $50 \mathrm{~km} / \mathrm{h}$. How many kilometres does she travel in 30 minutes?
(A) $30 \mathrm{~km}$
(B) $50 \mathrm{~km}$
(C) $25 \mathrm{~km}$
(D) $150 \mathrm{~km}$
(E) $100 \mathrm{~km}$
Since Lakshmi is travelling at $50 \mathrm{~km}$ each hour, then in one half hour (30 minutes) she will travel $50 \div 2=25 \mathrm{~km}$.