at maximum speed an airplane can travel 2460 miles against the wind in 6 hours. The plane can go the same distance, but with the wind in 5 hours. What is the speed of the plane with no wind?


5 Answers

Ray  Dart Profile
Ray Dart answered

Now you are asking us exam questions. Ask for help and you will get it (if we can help). Ask for an answer to an exam question and probably no-one will reply.

Virginia Lou Profile
Virginia Lou answered

Dear Allison Lee,

I think there is some information that is needed and it is not given to you... having to do with wind resistance, inertia, friction...

1. Can you just say, well, since it takes the plane 6 hours with a headwind and 5 hours with a tailwind, then it can fly the distance in 5.5 hours if there is no wind? If so, then your answer is 2460/5.5 = 447.3 mph.

2. Can you say, accurately, the same factor f will slow the plane with a headwind, and speed the plane in a tailwind? Then if S is the speed of the plane with no wind, you would get two equations:

headwind: S - f = 2460/6

tailwind: S + f = 2460/5. Then solving for S,

2S = 902

S = 451 mph.

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Jann Nikka
Jann Nikka commented
Dear Virginia, May I know the reason you always give students their homework answer? Wouldn't the teacher want the students to learn to solve their given assignments? Lastly how is given them the answers helping them learn? I'm just asking and curious. Thank you.
Tom  Jackson
Tom Jackson commented
The real issue is whether Virginia's answer is any more accurate than your usual answer of "42."
Tom  Jackson
Tom Jackson commented
And as Ray intentionally or unintentionally suggested, this may in fact be an "exam" rather than a "homework" question.
Jann Nikka Profile
Jann Nikka answered

As suggested you can find your homework answer if you do the work, your math book as hundreds of examples, work on several for a couple of hours, then work your question to a solution.

Tom  Jackson Profile
Tom Jackson answered

Consider this line of reasoning.

Against the wind, it takes 6 hours to go 2460 miles.  With the wind, the plane takes 5.5 hours to go 2460 miles.

Distance = (speed) * (time)

2 * 2460 = total distance or 4920 miles flown by plane in (how long?) 11.5 hours.

4920 miles / 11.5 hours = 427.8260869565217 miles / hour.

Did I eliminate the force of the wind as a factor or was it ever a factor in this particular problem ?

And this particular problem is at least a slightly tricky one. 

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Virginia Lou
Virginia Lou commented
Tom  Jackson
Tom Jackson commented
This is similar to where it takes me an hour to drive to a friend's house who lives 60 miles away. And then when I drive home in traffic it takes me 2 hours to get there.

Now, what is my average speed for the trip?
Deepak Suwalka Profile
Deepak Suwalka answered

let speed of wind be y mph
let speed of plane in still air be x
Against wind the speed = x-y
distance traveled = 2460
2460/x-y= 6
6x-6y= 2460
with wind speed = x+y
distance is same 2460

Add equation 1 & 2
x= 451 mph speed of plane in still air.
Plug the value of x in equation 1
y=40 mph the speed of wind

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