Here is the question

Question

 

A truck drove at an average rate of 45 miles per hour on the highway and 20 miles per hour once it entered the city. If it took the trip, which was 100 miles, in 3 hours, how much of it was in the city?

Answer 1

45h + 20c = 100

h + c  = 3  → h = 3 - c

 

45(3 - c) + 20c = 100

135 - 45c + 20c = 100

135 - 25c = 100

-25c = -35

c = 1.4

 

h = 3 - 1.75

h = 1.6

 

check:

45 * 1.6 + 20 * 1.4 = 100

72 + 28 = 100

100 = 100

So the truck spent 1.4 hours and 28 miles in the city.