To win a race, Ana needs to complete the last five kilometers in less than 20 minutes. What should her minimum speed be, in $\mathrm{km} / \mathrm{h}$?
Transforming minutes into hours, we have that 20 minutes correspond to 20/60 = 1/3 of an hour. Thus, Ana's speed must be greater than $v=5 / \frac{1}{3}=15 \mathrm{~km} / \mathrm{h}$.