Question 480182
Carlos and Maria drove a total of 258 miles in 5 hours. Carlos drove the first part of the trip and averaged 53 miles per hour. Maria drove the remainder of the trip and averaged 51 miles per hour. For approximately how many hours did Maria drive? Round answer to the nearest tenth if necessary. 
:
Let m = M's drive time
the total travel time was given as 5 hr, therefore
(5-m) = C's drive time
:
Write a distance equation, dist = speed * time
:
M's drive dist + C's drive dist = 258 mi
51m + 53(5-m) = 258
51m + 265 - 53m = 258
51m - 53m = 258 - 265
-2m = -7
m = {{{(-7)/(-2)}}}
m = +3.5 hrs is Marie's driving time
:
:
Confirm this by finding the actual dist each drove, (C drove 1.5 hrs)
51*3.5 = 178.5 mi
53*1.5 =  79.5 
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total d: 258; confirms our solution of m=3.5