Krishna Iyer, a motorist uses 24% of his fuel in covering the first 20% of his total journey (in city driving conditions). If he knows that he has to cover another 25% of his total journey in city driving conditions, what should be the minimum percentage increase in the fuel efficiency for non-city driving over the city driving fuel efficiency, so that he is just able to cover his entire journey without having to refuel? (Approximately)

• 43.48%
  
  Let there be 100 ltr. fuel and journey distance=100 km.
  Given, in city driving conditions, for first 20 km, 24 ltrs. fuel is used.
  So for next 25 km fuel required=24*25/20=30 ltrs.
  Thus, in city driving conditions, total journey=20+25=45 km & fuel used=24+30=54 ltrs.
  Fuel efficiency=45/54=5/6 km/ltr
  Now, remaining, 55 km is to be covered in 100-54=46 ltrs. Required fuel efficiency=55/46 km/ltr.
  Hence, % increase in the fuel efficiency=[(55/46 - 5/6)/(5/6)]*100=1000/23=43.48%
• 5 years agoHelpfull: Yes(3) No(0)