Jan and Kathy drove a total of 534 miles in 12.8 hours. Jan drove the first part of the trip and averaged 55 miles per hour. Kathy drove the second part of the trip and averaged 35 miles per hour. For what length of time did Jan drive?
Let t = time driven by J
then
(12.8-t) = time driven by K
Write a distance equation; distance = speed * time
J's distance + K's distance = 534 mi
55t + 35(12.8-t) = 534
55t + 448 - 35t = 534
55t - 35t = 534 - 448
20t = 86
t = 86/20
t = 4.3 hrs, J drove
Check solution, find the distance driven by each; K drove 12.8 - 4.3 = 8.5
55 * 4.3 = 236.5 mi
35 * 8.5 = 297.5
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total dist: 534
