Expert: Josh - 3/19/2006

Question
Lu Na's car gets 37 miles to the gallon on the highway. How many kilometers per liter does she get on the highway? Round to the nearest hundredth.

This is just a practice test anyway. But i am frustrated because I keep comming up with unreasonable answers.  

Answer
Bill,

Essentially, this question asks you to find the equivalence of 37 [miles]/[gallon] in terms of x [kilometer]/[litre].

To do this, you need to know the following:
1 gallon = 3.7854118 litre
1 mile = 1.609344 kilometer (km)

Looking at the ratio again, 37 [miles]/ 1 [gallon], the numerator may be replaced by 37 [mile]*1.609344 [km]/[mile] and expressed in terms of kilometers. The denominator may be replaced by 1 [gallon] * 3.7854118 [litre]/[gallon] and expressed in terms of litres.

Finally, we see that 37 [miles]/ 1 [gallon] = 37*1.609344 [km]/3.7854118 [litre].

Of course, we don't leave the answer like this, you reduce 37*1.609344/3.7854118 to a single number on a calculator. Rounding to the nearest hundredth means you are keeping 2 decimal points. If the third decimal figure is greater than or equal to 5, you round up the second decimal figure.

P.S. You may find this web site useful if you have to perform more unit conversions. http://www.metric-conversions.org/volume-conversion.htm