MathDB
Fuel Efficiency

Source: 2017 AMC 10B #12

February 16, 2017
AMCAMC 10AMC 10 Bpercent2017 AMC 10B

Problem Statement

Elmer's new car gives 50%50\% percent better fuel efficiency, measured in kilometers per liter, than his old car. However, his new car uses diesel fuel, which is 20%20\% more expensive per liter than the gasoline his old car used. By what percent will Elmer save money if he uses his new car instead of his old car for a long trip?
<spanclass=latexbold>(A)</span>20%<spanclass=latexbold>(B)</span>2623%<spanclass=latexbold>(C)</span>2779%<spanclass=latexbold>(D)</span>3313%<spanclass=latexbold>(E)</span>6623%<span class='latex-bold'>(A) </span> 20\% \qquad <span class='latex-bold'>(B) </span> 26\tfrac23\% \qquad <span class='latex-bold'>(C) </span> 27\tfrac79\% \qquad <span class='latex-bold'>(D) </span> 33\tfrac13\% \qquad <span class='latex-bold'>(E) </span> 66\tfrac23\%