Increasing the average speed of a car by 12 mph results in a 189 mile trip taking an hour less than before. What was the original average speed of the car?

Question

anonymous · Answer

46 I think

anonymous · Answer

how?

anonymous · Answer

189/x=189/(x+12)+1
189(x+12)=189(x)+x2+12x
189x+2268=189x+x2+12x
x2+12x-2268=0
(x+58)(x-46)=0
x=46 or -58
Throwing out the negative answer, we get the original speed of the car to be 46 mph..

anonymous · Answer

http://www.algebra.com/algebra/homework/word/travel/Travel_Word_Problems.faq.question.452586.html