Question 206637
Chris and leslie drove at total of 503 miles in 12.8 hours. 
Christ drove the first part of the trip and averaged 45 miles per hour.
 Leslie drove the remainder of the trip and averaged 35 miles per hour. 
For what length of the time did Chris drive?
:
Let t = time that Chris drove
then
(12.8 - t) = time Leslie drove
:
Write distance equation: Dist = speed * time
:
C's drive dist + L's drive dist = 503 mi
45t + 35(12.8 - t) = 503
:
45t + 448 - 35t = 503
:
45t - 35t = 503 - 448
:
10t = 55
t = {{{55/10}}}
t = 5.5 hrs, drive time of Chris
:
:
Check solution
12.8 - 5.5 = 7.3 hrs drive time of Leslie
Find the distances
45 * 5.5 = 247.5 mi
35 * 7.3 = 255.5
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total dist:503 mi; confirms our solution