“A steam locomotive consumes feedwater at 120  $\frac{\text{gal}}{\text{mi}}$ on level track. The scheduled run is 75 mi, and the tender holds 8,000 gal when full. Will one tender fill cover the run? If not, how many gallons short?”

Total water needed:  $120\frac{\text{gal}}{\text{mi}}\times 75\text{mi}=\mathrm{9,000}\text{gal}$.

Shortfall:  $\mathrm{9,000}-\mathrm{8,000}=\mathrm{1,000}\text{gal}$.

Answer: No; it’s short by 1,000 gal (needs a water stop).