In Europe, gasoline efficiency is measured in km/L. If your car's gas mileage is 38.0 mi/gal, how...

Question:

In Europe, gasoline efficiency is measured in {eq}\rm km/L {/eq}. If your car's gas mileage is {eq}\rm 38.0\ mi/gal {/eq}, how many liters of gasoline would you need to buy to complete a {eq}\rm 142\ km {/eq} trip in Europe?

Unit Conversions:

While certain English-to-metric unit conversions are easy to memorize, such as 2.54 cm to an inch, most necessitate a reference source. Though much of academia from elementary school to graduate school uses metric units, it is imperative to grow more accustomed to using English units as these are still the units in many US industries.

Unit conversions are most readily done by multipying or dividing and assigning the larger quantity a value of 1 to keep consistency. For example, there are 1.69 km in every mile and 3.785 L in one gallon. Next, start with the known quantity and multiply or divide to ensure that the correct units cancel out leaving only the desired units.

{eq}\left(\frac{38mi}{gal}\right) \cdot \left(\frac{1gal}{3.785L}\right) \cdot \left(\frac{1.69km}{1mi}\right) = 17.0 \tfrac{km}{L} {/eq}.

Next, divide the total mileage of the trip by the mileage to get the necessary quantity of liters.

{eq}\left(142km\right) \cdot \left(\frac{L}{17.0km}\right) = \boxed{8.4 L} {/eq}