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HeavyToilet
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I know how good you Pubbers are at math...
#5299490 - 02/14/06 02:46 PM (17 years, 11 months ago) |
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And I'm having a tough time figuring this question out... so I thought maybe someone could give me a hand with this question.
A barge moves at a rate of 7 km/h in still water. It travels 45km upriver and 45km downriver in a total time of 14 hours. What is the speed of the current?
I'm thinking you have to use the 'work principle' as they call it, but there are too many factors and I'm not sure how to put the equation together correctly.
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Prisoner#1
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299495 - 02/14/06 02:49 PM (17 years, 11 months ago) |
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the speed of the current is slower in the deep water... I hope that helps
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goobler
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299496 - 02/14/06 02:49 PM (17 years, 11 months ago) |
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2km/h
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HeavyToilet
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Re: I know how good you Pubbers are at math... [Re: goobler]
#5299511 - 02/14/06 02:53 PM (17 years, 11 months ago) |
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Care to enlighten me on the equation you used?
You didn't just guess at it, did you?
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TheCow
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Re: I know how good you Pubbers are at math... [Re: goobler]
#5299541 - 02/14/06 03:04 PM (17 years, 11 months ago) |
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Quote:
goobler said: 2km/h
Oh you devil
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goobler
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299585 - 02/14/06 03:20 PM (17 years, 11 months ago) |
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I used common sense
the current could not be >=7km/hr or the boat wouldnt go anywhere
bah I just knew...wanst hard
I'll look up the formula its not hard
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HeavyToilet
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Re: I know how good you Pubbers are at math... [Re: goobler]
#5299626 - 02/14/06 03:32 PM (17 years, 11 months ago) |
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Yeah well, on a test I'd really rather not have to rely on guessing.
There's a specific way of doing it and I just don't know how.
The Work Principle is
t/a + t/b = 1
Where t is the total time and... I don't really know what a and b should be. You'd have to somehow incorperate the distance, the speed, and the length of time. I just can't see how.
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lemon_lw
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299679 - 02/14/06 03:44 PM (17 years, 11 months ago) |
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read next post to figure out why i deleted this one
-------------------- In the belly of the Leviathan, one can either despair and perish, or be cheerful and persevere.-Dean Koontz
Edited by lemon_lw (02/14/06 03:54 PM)
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lemon_lw
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299693 - 02/14/06 03:49 PM (17 years, 11 months ago) |
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deleted out of shame
-------------------- In the belly of the Leviathan, one can either despair and perish, or be cheerful and persevere.-Dean Koontz
Edited by lemon_lw (02/14/06 04:11 PM)
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HeavyToilet
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Re: I know how good you Pubbers are at math... [Re: lemon_lw]
#5299701 - 02/14/06 03:51 PM (17 years, 11 months ago) |
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Nah the answer is 2.
Try plugging it in.
45/5 = 9 hours to get upstream 45/9 = 5 hours to get downstream, and added together is the total time, 14 hours.
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lemon_lw
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299706 - 02/14/06 03:52 PM (17 years, 11 months ago) |
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nope read my next post after that.
-------------------- In the belly of the Leviathan, one can either despair and perish, or be cheerful and persevere.-Dean Koontz
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minesstudent
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Re: I know how good you Pubbers are at math... [Re: lemon_lw]
#5299716 - 02/14/06 03:54 PM (17 years, 11 months ago) |
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t1+t2=12 and (x+c)t1=45 and (x-c)t2=45 where x is your speed, c is the current and t1 and t2 are the two times. Solve for the varables. Thats how I used to do it in algebra two. I wouldn't have remembered though if it wasn't for the above post. I think this is a little clear though.
-------------------- "The universe is the way it is because if it wasn't we wouldn't be here to talk about it"
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HeavyToilet
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Re: I know how good you Pubbers are at math... [Re: lemon_lw]
#5299718 - 02/14/06 03:54 PM (17 years, 11 months ago) |
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It can be solved. You'd be right if we weren't given the total time it takes. For example, it the current was 6, it would take 45 hours to get upstream.
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riby
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299734 - 02/14/06 03:58 PM (17 years, 11 months ago) |
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yep, it's two
Edited by riby (02/14/06 03:59 PM)
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lemon_lw
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299743 - 02/14/06 04:01 PM (17 years, 11 months ago) |
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ok its official my math skills have went to shit.
-------------------- In the belly of the Leviathan, one can either despair and perish, or be cheerful and persevere.-Dean Koontz
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HeavyToilet
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299747 - 02/14/06 04:02 PM (17 years, 11 months ago) |
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It's impossible to solve if there are two variables. Do you know a way of reducing it to only one variable? Because I'm still having problems.
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TheCow
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299753 - 02/14/06 04:03 PM (17 years, 11 months ago) |
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Its a system of equations.
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goobler
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Re: I know how good you Pubbers are at math... [Re: TheCow]
#5299786 - 02/14/06 04:09 PM (17 years, 11 months ago) |
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I R TEH WINAR!
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minesstudent
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299790 - 02/14/06 04:09 PM (17 years, 11 months ago) |
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Goddamnit I just solved that problem for the current speed of 7 not the boat. If your interested the boat would have to go 11.69 to do it in that time with that current
-------------------- "The universe is the way it is because if it wasn't we wouldn't be here to talk about it"
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HeavyToilet
The Heaviest OfThem All


Registered: 08/06/03
Posts: 9,458
Loc: British Columbia
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299800 - 02/14/06 04:11 PM (17 years, 11 months ago) |
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Well how did you do it? Perhaps I can modify what formula you used.
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minesstudent
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299810 - 02/14/06 04:13 PM (17 years, 11 months ago) |
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You actually use 3 equations with 3 unknowns in my equations, I'm not sure how right it is as I haven't quite used to solve anything yet.
-------------------- "The universe is the way it is because if it wasn't we wouldn't be here to talk about it"
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HeavyToilet
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Registered: 08/06/03
Posts: 9,458
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299871 - 02/14/06 04:26 PM (17 years, 11 months ago) |
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I'm desperate here, any lead I can follow up on I will.
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minesstudent
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299879 - 02/14/06 04:27 PM (17 years, 11 months ago) |
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nevermind, my system is wrong there is an eazier way. I can't even use my system to solve it. I repeat don't use mine. theoretically it should work but I can't even figure out how to solve it. Sorry
-------------------- "The universe is the way it is because if it wasn't we wouldn't be here to talk about it"
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Prisoner#1
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299917 - 02/14/06 04:33 PM (17 years, 11 months ago) |
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Quote:
minesstudent said: nevermind, my system is wrong
thats why I listen to goobler, he's never wrong he thought he was wrong once but he was mistaken
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minesstudent
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5299956 - 02/14/06 04:39 PM (17 years, 11 months ago) |
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Using my ti-89 I got that current is -2.753 which I know is wrong. I tried but I don't remember algebra 2 for the life of me. You forget it when you start doing calculas. Sorry man I tried, 2 is right I just can't figure out the formula to use.
-------------------- "The universe is the way it is because if it wasn't we wouldn't be here to talk about it"
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phalloidin

Registered: 07/03/04
Posts: 865
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5299960 - 02/14/06 04:40 PM (17 years, 11 months ago) |
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45/(7+c) + 45/(7-c) = 14
multiply both sides by (7+c)(7-c)
45(7-c) + 45(7+c) = 14(49-c^2)
then solve for c
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HeavyToilet
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Re: I know how good you Pubbers are at math... [Re: phalloidin]
#5299984 - 02/14/06 04:47 PM (17 years, 11 months ago) |
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Holy shit man you did it, thanks a lot. 5 Shrooms to you, and eternal gratefulness.
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minesstudent
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Re: I know how good you Pubbers are at math... [Re: HeavyToilet]
#5300011 - 02/14/06 04:53 PM (17 years, 11 months ago) |
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Shit I feel like a retard now. I did that excact thing but missed a sign and got a square of a negative number and it didn't work.
-------------------- "The universe is the way it is because if it wasn't we wouldn't be here to talk about it"
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phalloidin

Registered: 07/03/04
Posts: 865
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Re: I know how good you Pubbers are at math... [Re: minesstudent]
#5300032 - 02/14/06 04:58 PM (17 years, 11 months ago) |
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ha, I actually started working it a harder way i used two equations and two unknowns (7+c)t=45 (7-c)(14-t)=45 I think that should work, but the math got a little funky then I looked at it again and saw a much easier way
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