SOLUTION: jJoe and Louise are making a drive from San Diego to Salt Lake City. After 4 hours of driving, they are 507 miles from Salt Lake City. Eight hours into their trip, they are only 26

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: jJoe and Louise are making a drive from San Diego to Salt Lake City. After 4 hours of driving, they are 507 miles from Salt Lake City. Eight hours into their trip, they are only 26      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 884616: jJoe and Louise are making a drive from San Diego to Salt Lake City. After 4 hours of driving, they are 507 miles from Salt Lake City. Eight hours into their trip, they are only 267 miles away from their destination. Assume they averaged the same speed for the entire trip.
Question 1. In how many hours will they reach Salt Lake City from time they left San Diego?
2. How far from Salt Lake City will they be after 10 hours of driving?
3. When will they be 300 miles from Salt Lake City?
4. What is the distance from San Diego to Salt Lake City?
Please help me..
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Main goal is to find the average speed of travel and the distance from San Diego to Salt Lake City.
r = average speed
d = trip distance between the cities.

First Part:
r%2A4=d-507

Second Part:
r%2A8=d-267

Last Part:
We do not yet know but we can find what we need after we solve for r and d.

SYSTEM OF EQUATIONS
highlight_green%284r-d=-507%29 and highlight_green%288r-d=-267%29.
Elimination Method to Eliminate d.
-
8r-d-%284r-d%29=-267-%28-507%29
4r%2B0=507-267
highlight%28r=60%29.
-
Either equation to find d,
d=8r%2B267
d=8%2A60%2B267
d=480%2B267
highlight%28d=747%29

Using what was found in solving for r and d, the four questions are simpler to answer.