SOLUTION: I have been working on this problem and I have tried it many times and I still can't figure it out. I was wondering if someone could help me? I would deeply appreciate it! Please a

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Question 156250This question is from textbook Algebra and Trigonometry Structure and Method book 2
: I have been working on this problem and I have tried it many times and I still can't figure it out. I was wondering if someone could help me? I would deeply appreciate it! Please and Thank You!!!
A subway train makes six stops of equal length during its 21 km run. The train is actually moving for 20 min of the trip. At most how long can the train remain at each station if the average speed for the trip, including stops, is to be at least 36 km/h?
This question is from textbook Algebra and Trigonometry Structure and Method book 2

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A subway train makes six stops of equal length during its 21 km run. The train is actually moving for 20 min of the trip. At most how long can the train remain at each station if the average speed for the trip, including stops, is to be at least 36 km/h
:
Convert 20 min to 1%2F3 hr
:
Let s = duration of the stop in hrs
:
Write a speed equation: speed = dist%2Ftime
:
21%2F%28%286s%2B%281%2F3%29%29%29 => 36
:
21 => 36(6s+1%2F3)
21 => 216s + 12
;
21 - 12 => 216s
:
216s <= 9
Convert hrs to minutes
s <= 9%2F216 * 60
s <= 2.5 min per stop to average 36 km.hr or greater
:
Check solution
Total time 6(2.5) + 20 = 35 min
:
Find the distance
35%2F60 * 36 = 21 km confirms our solution