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Speeding up


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159 replies to this topic

#21 fnramly

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Posted 01 July 2007 - 08:18 AM

I will drive with speed 1800Km/Hours or above.
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#22 Camshaft

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Posted 03 July 2007 - 04:25 PM

So why can't you just drive at 90km/hour for one hour and at the end of that hour you end up at your destination? Reading the question I don't see any rules against doing this.
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#23 lukegaru

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Posted 03 July 2007 - 08:22 PM

can't be done you've already used your hour
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#24 Incognitum

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Posted 04 July 2007 - 11:29 AM

can't be done you've already used your hour



These is no time limit posted in the question! Who's hour did you use?!?! Oh no, it's not like there is another hour coming right after this one or anything! Jeez, when you guys get a notion into your head...

Is the object of these puzzles to get you to give up, or to think in perpendicular directions?

I submit that an answer which is reasonable and violates no premises of the question is a proper resolution to the question. If you do not agree, please tell me specifically which conditions will cause the question to be regarded as solved.
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#25 Incognitum

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Posted 04 July 2007 - 11:37 AM

THATS FUNNY. REDICULOUS AT BEST. "WARP" lol,,, "While your at it, just hook up a Flux-Capacitor" to your forehead and run 88 MPH Backwards, and maybe you can GO BACK IN TIME and just travel 60 the entire trip" Clowns....

"Humbug to Reality Void Answers"




Apparently you have trouble recognizing sarcasm, maybe you should consult an optometrist...

But just to clue you in, the point of the post was to support a detour solution, and the other two suggestions were for humorous effect.


Just FYI, a flux capacitor would be no good at all, it would take you back to the FUTURE, not the past... <--- That's a joke
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#26 youareallwrong

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Posted 04 July 2007 - 10:44 PM

you guys are all wrong. The answer is 60 because it says how fast will you have to drive for THE REST OF THE WAY to be an average of 60. not the whole way.
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#27 Incognitum

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Posted 04 July 2007 - 11:00 PM

you guys are all wrong. The answer is 60 because it says how fast will you have to drive for THE REST OF THE WAY to be an average of 60. not the whole way.



Here's a riddle for you: "If you've read half the question at 30 WPM, how much of the rest of the question do you need to read to understand what we are talking about?"



If I go halfway to the town (which is 60 km away) at the speed of 30 km/hour, how fast do I have to go for the rest of the way to have the average speed of the entire way 60 km/hour?


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#28 elduderino2085

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Posted 05 July 2007 - 05:54 AM

I believe the answer is indeed 90km per hour. The question does not state that there is a limit placed on the amount of time one must take to get from one point to the other, which means all one must do is speed up in order to average 60km per hour overall. It does not state that one must travel between the two points within 1 hour. Perhaps the answer was meant to be something different, but as far I as I can tell the question was not phrased in such a way. So here is my logic in bullet form:

There are two points spaced 60km apart

You travel halfway at 30km/h

To average 60km/h you must travel at 90km/h to make up the initial sluggishness

Having done so, you have now traveled 60km and averaged 60km/h

This seems correct to me.
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#29 Incognitum

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Posted 05 July 2007 - 10:03 AM

I believe the answer is indeed 90km per hour. The question does not state that there is a limit placed on the amount of time one must take to get from one point to the other, which means all one must do is speed up in order to average 60km per hour overall. It does not state that one must travel between the two points within 1 hour. Perhaps the answer was meant to be something different, but as far I as I can tell the question was not phrased in such a way. So here is my logic in bullet form:

There are two points spaced 60km apart

You travel halfway at 30km/h

To average 60km/h you must travel at 90km/h to make up the initial sluggishness

Having done so, you have now traveled 60km and averaged 60km/h

This seems correct to me.



Yeah, here is the part your not quite getting: the average is not calculated by speed over distance. Your model produces an average of 60(km/h)/km. The average we're looking for is calculated by distance over time(km/h). Because 90km/h is faster then 30km/h it takes less time to cover the distance remaining. So you are going slow for a long time, and fast for a short time. So you don't get to spend 30 minutes at 90mph to bring the average up if you are traveling in a straight line. To spend 30 minutes at 90km/h you must overshoot your mark by 15km. I hope that helps clear things up a little.

Maybe this will help illustrate the point: A kayak and a motor boat have a race up river two knots and back down to the starting place (total of 4 knots in the race). The motor boat travels at 2 knots per hour both directions, but the kayak travels at 1 knot per hour upstream, and 3 knots per hour downstream. Who wins the race?
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#30 wellteased

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Posted 10 July 2007 - 05:59 AM

A good brain teaser stretches your imagination and helps break the tendency to automatically think in mundane linear patterns.

I believe the intended solution to this puzzle is that it is not possible.

However the "wait a minute, who says you only have one hour." concept also qualifies ...especially if you consider it after recognizing the intended solution.

There is a difference between nitpicking over how well or poorly the question is written, and having fun considering the possible alternate solutions. Learning to recognize the intended solution despite possible flaws in the wording is an important skill. (And will help your grades)
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