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crapflinger2000

brain teaser

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You have decided to take a morning run to prepare for the local marathon at an average speed of 6 miles per hour. Unfortunately, you are not in as good shape as you thought, and you are running uphill. You find that for the first half of the run, all uphill, your average speed was only 3 miles per hour. How fast must you run on the way back, all downhill, to make for an entire round trip average speed of 6 miles per hour?
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1) Morning run...Not factoring in temperature variations, wind velocity, or resistance that might elongate the distance....just a "strait forward math problem"

2) "You find that for the first half of the run" = equal time (ie 1/2 of run @ 3 MPH and the second 1/2 of run at xMPH)

3) Distance is irrelavent(sp)

4) So... if 1st half of run is say given a value of 1 hour, then the distance travelled is 3 miles.

5) if 6 miles an hour is the average that we are trying to achieve then we must run at 9MPH for tyhe next hour to cover 9 miles.

6) IF that is accomplished, then 3 miles in the first hour, and 9 miles in the second hour, is 12 miles in a two hour run...right? Last time I checked if you went 12 miles in two hours, the average was 6 miles an hour.

7)Now that I have wasted my time typing this, you are going to tell me that you meant distance not time...which in effect does make me 1/2 right.

I'm not usually into the whole 3-way thing, but you got me a little excited with that. - Skymama
BTR #1 / OTB^5 Official #2 / Hellfish #408 / VSCR #108/Tortuga/Orfun

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7mph. I'm guessing since you're only 1/2 way there, you still have to keep going another half and then come back. But, since you're out of shape, it may not be possible.

--------------------------------------------------
the depth of his depravity sickens me.
-- Jerry Falwell, People v. Larry Flynt

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you can't

say it's a 24 mile round trip.
average 6mph and it takes 4 hours

halfway is 12 miles
12 miles at 3 mph is already 4 hours.

you're skrewed



WE HAVE A NEW BIG BRAIN WINNER and fast two: My explaniation is basically the same as Cindy....

You can't do it at all. If your run is 6 miles, you would have to do it in one hour to average 6 miles per hour. However, you've already taken an hour to do the first half of the run, thereby using all the available time and there for your out of luck... cant be done.

Want another one?????

Scott C.
"He who Hesitates Shall Inherit the Earth!"

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you can't

say it's a 24 mile round trip.
average 6mph and it takes 4 hours

halfway is 12 miles
12 miles at 3 mph is already 4 hours.

you're skrewed



WE HAVE A NEW BIG BRAIN WINNER and fast two: My explaniation is basically the same as Cindy....

You can't do it at all. If your run is 6 miles, you would have to do it in one hour to average 6 miles per hour. However, you've already taken an hour to do the first half of the run, thereby using all the available time and there for your out of luck... cant be done.

Want another one?????

Scott C.



OK, look Mr. Smartypants, if you're gonna be all brainiacal with us, you gotta at least specifiy that "half the run" refers to half of a set time limit as opposed to distance. Last I checked, marathons didn't have time limits.

:P

Alright, alright, gimme another one...

you've got to ask yourself one question: 'Do I feel loquacious?' -- well do you, punk?

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so, I was right, you were talking distance as well.
if you separate the time/distance thing you can do it.
it is simple averages then.
I'm not usually into the whole 3-way thing, but you got me a little excited with that. - Skymama
BTR #1 / OTB^5 Official #2 / Hellfish #408 / VSCR #108/Tortuga/Orfun

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You have decided to take a morning run to prepare for the local marathon at an average speed of 6 miles per hour. Unfortunately, you are not in as good shape as you thought, and you are running uphill. You find that for the first half of the run, all uphill, your average speed was only 3 miles per hour. How fast must you run on the way back, all downhill, to make for an entire round trip average speed of 6 miles per hour?



A marathon is 26.2 miles.

26.2 miles / 2 = 13.1 miles

13.1 miles / 3 mph = 4.3666 hrs.

26.2 miles / 6 mph = 4.3666 hrs.

Therefore you must run infinately fast back to the starting line.
quade -
The World's Most Boring Skydiver

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OK, look Mr. Smartypants, if you're gonna be all brainiacal with us, you gotta at least specifiy that "half the run" refers to half of a set time limit as opposed to distance. Last I checked, marathons didn't have time limits.

:P

Alright, alright, gimme another one...



You have to average X-mph over a run. Time and distance are there to help figure out the answer but not completely relvant to the answer as different values can be used to determine the answer. No matter what the distance is, if you go 1/2 X-mph of the target for the first half unless you can instantly go back to the start you cant get back in time to average X-mph for the entire run.....no matter whatthe distance

Now for another one, non-math this time......

Dalton likes pots and pans but not cooks. He likes straw but not hay; he likes sagas but not poems. Does he like a star or a planet?

Scott C.
"He who Hesitates Shall Inherit the Earth!"

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But he specified the "first half of the run" right...that means that you run 1)equal amounts of time, 2)equal amounts of distance, or 3) a combination of the two.

anyway...

it's all in the symantics of it.
I'm not usually into the whole 3-way thing, but you got me a little excited with that. - Skymama
BTR #1 / OTB^5 Official #2 / Hellfish #408 / VSCR #108/Tortuga/Orfun

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Proper parameters? Everything was there! It clearly said "marathon".



Actually, it said "prepare for the local marathon."

--------------------------------------------------
the depth of his depravity sickens me.
-- Jerry Falwell, People v. Larry Flynt

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Rats, I don't like that other problem...

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Dalton likes pots and pans but not cooks. He likes straw but not hay; he likes sagas but not poems. Does he like a star or a planet?



This one, I can handle: he likes a star.

B|

you've got to ask yourself one question: 'Do I feel loquacious?' -- well do you, punk?

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Here is an oldy but goody.

Put away your calculator and figure this one out in your head.

How many zeros are there at the end of 100! (factorial)?

That means 1x2x3x4x5...x98x99x100

This one was often asked during interviews to see how someone approached a new problem.
~Cindy~

"I dont know what your problem is, but I'll bet its hard to pronounce."

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it's all in the symantics of it.



Yes. It is.

In order to run 26.2 miles (a marathon) at an average speed of 6 mph, it will take 4.3666 hours.

Since he said the half-way mark was up the hill and accomplished at 3 mph and that the remaining distance was back to the point at which the runner started (to complete the round trip), one can ONLY assume that the half-way mark was refering to a distance and not a time. The time it took must be inferred by the distance and the speed -- which in this case happens to be exactly what the orginally stated goal time of 4.3666 hours was.

There's no other logical way of looking at the problem.
quade -
The World's Most Boring Skydiver

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Dalton likes a star. He only likes words that also spell words backwards.

Dalton likes pots (stop) and pans (snap) but not cooks (skooc). He likes straw (warts) but not hay (yah); he likes sagas (sagas) but not poems (smeop). Does he like a star (rats) or a planet (tenalp)

Nice job Rebecca

Scott C.
"He who Hesitates Shall Inherit the Earth!"

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B| uh thank you, thankyouverymuch.

Wow! it feels so good to finally have gotten one right! No semantics, no argument, it's so refreshing being up here in the smart echelon...
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GAGHHHHH!!! I CAN'T DO IT!!! I CHEATED! I GOOGLED THE DAMN THING! I'm sorry! I just wanted to win one, too...

I suck. Can y'all forgive me?


Jeez- I am a rotten liar. I don't even know most of you, and I couldn't do it...

you've got to ask yourself one question: 'Do I feel loquacious?' -- well do you, punk?

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