A car's fuel efficiency is 30 miles per gallon. Which of the... | SAT Ratios, rates, proportional relationships, and units Question, Answer Explained

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Math · Problem-Solving and Data AnalysisHard

A car's fuel efficiency is $30$ miles per gallon. Which of the following is closest to the car's fuel efficiency in kilometers per liter? (Use $1$ mile $= 1.609$ kilometers and $1$ gallon $= 3.785$ liters.)

$4.9$

$12.8$

$70.6$

$182.7$

Show answer and explanation

Answer: B

On $1$ gallon the car travels $30$ miles, which is $30 \times 1.609 = 48.27$ kilometers. One gallon is $3.785$ liters, so the car travels $\frac{48.27}{3.785} \approx 12.8$ kilometers per liter.

Choice C multiplies by $3.785$ and divides by $1.609$ , which converts both units in the wrong direction.

Why the other choices are wrong

A. This divides 30 by both 1.609 and 3.785. Miles must be multiplied by 1.609 to get kilometers.
C. This multiplies by 3.785 and divides by 1.609, which converts both units in the wrong direction.
D. This multiplies by both conversion factors. The liters belong in the denominator, so divide by 3.785.

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