Question
Shari drove for 90 miles in the city. When she got on the highway, she increased her speed by 20 mph and drove for 130 miles. If Shari drove a total of 4 hours, how fast did she drive in the city?
Answers
(90 / c) + [130 / (c + 20)] = 4
90 c + 180 + 130 c = 4 c^2 + 80 c
c^2 - 35 c - 45 = 0
use quadratic formula to find c
90 c + 180 + 130 c = 4 c^2 + 80 c
c^2 - 35 c - 45 = 0
use quadratic formula to find c
typo error in 90 c + 180 + 130 c = 4 c^2 + 80 c
should be : 90 c + 1800 + 130 c = 4 c^2 + 80 c
---> c^2 - 35c - 450 = 0
(c - 45)(c + 10) = 0
c = 45 or a negative
city speed was 45 mph
should be : 90 c + 1800 + 130 c = 4 c^2 + 80 c
---> c^2 - 35c - 450 = 0
(c - 45)(c + 10) = 0
c = 45 or a negative
city speed was 45 mph
thanks for the catch, Reiny
too late to be working on this stuff
too late to be working on this stuff
Related Questions
According to a rating agency, a car's MPG (miles per gallon) ratings are: 25 MPG for city and 30 MPG...
Millwood city is constructing a new highway through town. The construction crew can complete 5 3/6 m...
Mark's house is 90 miles away from New York. You travel 15 miles on city streets, and then 75 miles...
The city to highway fuel economy on the new car I just bought is 25:32. Yesterday, I drove 123 miles...