1) In his old car: number of gallons per year = 16000/20 = 800 gallos cost of fuel per year = 800 x $3.2 = $2560
2) In his new car, the mileage of 16000 remains the same and the cost per gallon $3.2 also. I he made a saving of $ 675, that means only the mileage per gallon changed from 20 mi/gal to x mi/gal. (x certainly is greater than 20). So we have to calculate the new mileage. Let x be the NEW mileage/gallon: a) Number of gallon per year = 16000/x b) Cost of few per year = (16000/x).(3.2) = (2560 - 675)
= (48000/x)= 1825 (cross multiplication) → x = 48000/1825 and x = 26.3 mi/gal (NEW mi/gal)
Then, with his new car he gained 26.3 - 20 = 6.3 mi/gal (more tan with his old car)
= 144