Please Help - one question

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rabia

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Aug 28, 2009
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the question is:

A jet flew from Tokyo to Bagkok, a distance of 4800 km. On the return trip, the speed was decreased by 200 km/h. If the difference in the times of the flight was 2 h, what wast the jet;s speed from Bangkok to Tokyo?

here is what i have so far..its not much

Let x represent the speed in km/h from Bangkok to tokyo

Since speed is decreased by 200 km/h on return trip, then x-200 represents the speed from Bangkok to toyko

d=st => t = d/s
d=distance
s=speed
t=time

table first:

----------------------------------- Distance (Km) ------ Speed(km/h) ------ Time (h) => t=d/s
Bangkok to Toyko ------------------------ 4800 ------------------- x ------------------- 4800/x
Tokyo to Bangkok ---------------------- 4800 ------------------ x-200 --------------- 4800/x-200 (2) ===> (not sure where to put that 2 hrs delay

next part:

i know how i would set it up but i am not sure if i am doing it correct or what should i let the equation equal

4800 / x + 4800 / x-200 or 4800 / x + 9600/x-400

after set it up i know i would have to find the common denominators and go from there, but i am stuck right here, i am having trouble set up the equation to slove for x.

Some one please Help..

Thanks
 
rabia said:
… Let x represent the speed … from Bangkok to tokyo …

… then x-200 represents the speed from Bangkok to toyko …
Click to expand...


Hello Rabia:

Do you see a problem with the two statements above?

Also, you've twisted the speeds around in your chart.

The jet flew from Tokyo to Bangkok first; the return trip is Bangkok to Tokyo.

Otherwise, you're doing okay.

The 2 hours is not a "delay".

When the speed of the jet was decreased, the return trip took longer.

The word "difference" means it took 2 hours longer.

In other words, if we subtract the shorter time from the longer time, the difference must be 2.

4800/(x - 200) - 4800/x = 2

Journey onward!

Cheers,

~ Mark 8-)

MY EDIT: Corrected typographical error noted by Bill, thank you.
 


I corrected my typo. :oops:

Also, I suppose that the 2 hours could be thought of as a delay, if the airline advertised the same flight time for both arrivals.

8-)

 
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