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?

Answer 1

(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

Answer 2

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

Answer 3

thanks for the catch, Reiny

too late to be working on this stuff