SOLUTION: Sheri drove southeast from Albuquerque to Roswell and then South to Carlsbad. She averaged 75mph along the route to from Albuquerque to Roswell and averaged 70mph from Roswell to C

Question 141704: Sheri drove southeast from Albuquerque to Roswell and then South to Carlsbad. She averaged 75mph along the route to from Albuquerque to Roswell and averaged 70mph from Roswell to Carlsbad. She covered the entire 220 miles in 3 hours. How long did she take to drive from Albuquerque to Roswell.
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
Sheri drove southeast from Albuquerque to Roswell and then South to Carlsbad. She averaged 75mph along the route to from Albuquerque to Roswell and averaged 70mph from Roswell to Carlsbad. She covered the entire 220 miles in 3 hours. How long did she take to drive from Albuquerque to Roswell.
:
Solve this with two unknowns
:
Let t = time from A to R
Let d = dist from A to R
and
(3-t) = time from R to C
(220-d) = dist from R to C
:
Dist = speed * time
:
Dist, A to R:
d = 75t
:
Dist, R to C
70(3-t) = 220 - d
210 - 70t = 220 - d
:
Substitute 75t for d. solve for t
210 - 70t = 220 - 75t
+75t - 70t = 220 - 210
5t = 10
t =
t = 2 hrs from A to R
:
:
check solution by finding the distances (R to C time = 1 hr):
2*75 = 150 mi
1*70 = 70 mi
-------------
total: 220 mi
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