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A plane flies from Penthaven to Jackson and then back to Penthaven. When there is no wind, the round trip takes 3 hours and 36 minutes, but when there is a wind blowing from Penthaven to Jackson at  30 miles per hour, the trip takes 3 hours and 45 minutes. How many miles is the distance from Penthaven to Jackson?

(Assume that the plane flies at a constant speed, and that the turnaround time is negligible.)

 Jul 5, 2023
 #1
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Let the distance between Penthaven and Jackson be d miles. Let the speed of the plane in still air be s miles per hour.

When there is no wind, the plane flies from Penthaven to Jackson at speed s and then back at the same speed. The total time for the round trip is 2d/s hours.

When there is wind, the plane flies from Penthaven to Jackson at speed s+30 miles per hour and then back at speed s−30 miles per hour. The total time for the round trip is 2d/(s+30)+2d/(s−30) hours.

We are given that the round trip time with no wind is 3 hours and 36 minutes, or 198/60 hours, and the round trip time with wind is 3 hours and 45 minutes, or 210/60 hours. Setting these two equations equal to each other, we get:

s2d​=60198​ands+302d​+s−302d​=60210​.

Solving these equations, we find that s=250 miles per hour and d=800 miles.

Therefore, the distance between Penthaven and Jackson is 800​ miles.

 Jul 5, 2023
 #2
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its wrong

 Jul 5, 2023
 #3
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Pls explain why you say it's wrong

Guest Jul 6, 2023
 #4
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D==Distance (one way),    S ==Speed in mph

 

2D / S ==3.6...........................................(1)  

D / [S - 30] + D/[S + 30]==3.75............(2), solve for D, S

 

D==270 miles - one way from Jackson to Penthaven.

S ==150 mph - speed of the plane in still air.

 Jul 6, 2023

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