Which quantities could be measured
to determine the fuel efficiency of a car?
Fuel efficiency is a kind of
ratio. It’s a ratio of the fuel used to
the distance travelled with that amount of fuel. Option a) says the distance
travelled over a good period.
There’re really two problems
here. The first problem is that this is a
ratio of distance to time, meaning it’s not a ratio of fuel used to distance
travelled. And the second problem is “over a
good period” is a nonspecific amount of time. So a) is not the option we’re
b) The quantity of fuel used. The quantity of fuel used would
tell us the quantity of fuel used. But it’s not a ratio. And that means it’s not a measure
of efficiency. c) The fuel price and the distance travelled. There’s no direct correlation
between the price that you pay for the fuel and the distance you’re able to
And finally option d), the distance
travelled and the corresponding volume of fuel used. This is what we’re looking for. We wanna know the ratio of how far
you go and the corresponding amount of fuel used to go that far.
With that in mind, let’s consider
which of the following is an appropriate unit for measuring fuel efficiency. Remember, this ratio is the
distance travelled and the volume of fuel used. a) says cubic centimetres per a
litre. Cars do not travel in cubic
centimetres. Cubic centimetres is a volume.
And we’ll have the same problem
with option b), cubic centimetres per gallon. Again, cars can’t travel by cubic
centimetre. Option c) kilometres per hour. Well, cars do travel in
kilometres. However, we don’t measure volume of
fuel in hours. Miles per hour is option d). Cars can travel in miles. But again hour is not a measure of
Our last option is correct, miles
per gallon. Distance travelled, miles, is being
compared to the volume of fuel used, gallons.