Question

Sarah drove her car a distance of 650.8 km, and used 39.5 L of gasoline (petrol). What is her fuel efficiency in miles per gallon (

)?
Use the following facts:

1 km = 0.6214 mi
1 gal = 3.8 L

Round your answer to the nearest tenth.

Answer 1

2.7 miles/gallon

Explanation:

How Do You Calculate Efficiency?

Efficiency can be expressed as a ratio by using the following formula: Output ÷ Input. Output, or work output, is the total amount of useful work completed without accounting for any waste and spoilage. You can also express efficiency as a percentage by multiplying the ratio by 100.

650.8/39.5 = 16.5

0.6214 x 650.8 = 404.4

3.8 x 39.5 = 150.1

404.4/150.1 = 2.69420386409

Answer 2

Explanation:

Use dimensional analysis for this. Set up the unit multipliers so that top labels cancel with bottom labels in your conversions.

`(650.8km)/(39.5L)*(.6214mi)/(1km)*(3.8L)/(1gall)`

What happens is that the label of km with the 650.8 cancels with the one under the .6214; likewise, the L by the 39.5 cancels with the one by the 3.8, leaving us with miles/gallon. Multiply straight across the top and straight across the bottom to get

`(1536.747056mi)/(39.5gall)`

and then divide to get 38.9 miles/gallon