Sophie drove 225 mi south through the Smoky Mountains. Snow during her return trip made her average speed on the return trip 30 mph slower. The total driving time was 8 hr. Find Sophie’s average sped on each part of the trip.

Question

anonymous · Answer

@Nnesha

jim_thompson5910 · Answer

let x = speed on her first part of the trip

x-30 is the speed on the second part of her trip coming back

jim_thompson5910 · Answer

d = r*t
225 = x*t
t = 225/x is the time it takes to drive 225 mi at x mph


d = r*t
225 = (x-30)*t
t = 225/(x-30) is the time it takes to drive 225 mi at x-30 mph

combine the two times and set that equal to 8

$$\Large \frac{225}{x}+\frac{225}{x-30} = 8$$

now solve for x