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 09-16-2009 #1 (permalink) Benevolent Misfortune ♠ Games Awards   Join Date: Jun 2008 Location: Texas Posts: 3,470 iTrader: (0) IGN: Sanichi Class: Scholar Level: 50 Guild: FrenchBread Solve for x and y: System of Equations I have a problem I need help working out considering I am not much of an expert on such questions. Does anyone know how to such system of equations? The Word Problem is: A zookeeper needs to mix feed for the prairie dogs so that the feed has the right amount of protein. Feed A has 12% protein. Feed B has 5% protein. How many pounds of each does he need to mix to get 100 pounds of feed that is 8% protein. I believe equation to solve is: x+y=100 100(.8)=x(.12)+y(.05) But I am not sure how to work it out with going overly-broad with working it out. __________________ / / / Playing:Tree of Savior
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 09-16-2009 #2 (permalink) Apple is A Games   Join Date: Oct 2007 Location: none yo business Posts: 1,412 iTrader: (0) IGN: CarmelSan Class: Eir Guild: OurStory a + b = 100 .12a +.05b = .8? Did you mean 80% of protein? and then solve and whatnot "100(.8)=x(.12)+y(.05)" actually what does this mean? are the numbers in the paren. in place for the 2nd equation? __________________ How sexy. <3 Last edited by Laughatyou21; 09-16-2009 at 05:51 PM.
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Quote:
 Originally Posted by Laughatyou21 x + y = 100 .12x +.05y = .8? Did you mean 80% of protein? and then solve and whatnot "100(.8)=x(.12)+y(.05)" actually what does this mean? are the numbers in the paren. in place for the 2nd equation?
The numbers in parenthesis are being multiplied to the variable.

Give me a minute. I'm gonna write and scan my solution. I hate typing it up.
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 09-16-2009 #4 (permalink) Apple is A Games   Join Date: Oct 2007 Location: none yo business Posts: 1,412 iTrader: (0) IGN: CarmelSan Class: Eir Guild: OurStory I dun think you can multiply 100 by .8 if there's no variable to substitute the .8 in. fml, well w/e, I was never good with system of equations. __________________ How sexy. <3
 09-16-2009 #5 (permalink) [夢] Games   Join Date: Jun 2008 Posts: 1,486 Blog Entries: 5 iTrader: (0) IGN: Yume/Relief/夢 Guild: Drop/JW/Kirameki/Hores(FT) x+y=100 100(.8)=x(.12)+y(.05) Uh, from what I think... the second equation should be 100(.08)=x(.12)+y(.05) to solve for x and y, take your first equation x+y=100, and rewrite it as y=100-x and then put this into your second equation so 100(.8)=x(.12)+(100-x)(.05) 8=.12x+5-.05x solve for x then when you have x, put it in for x+y=100 to figure out y if it's not this, then I don't know /o/ __________________ "Even a broken clock is right twice a day."
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Quote:
 Originally Posted by Laughatyou21 I dun think you can multiply 100 by .8 if there's no variable to substitute the .8 in. fml, well w/e, I was never good with system of equations.
Oh whoops, didn't see that part.
No wonder it looked so weird on paper.

Anyone else getting -60 lbs. for Feed A?
`-`
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Last edited by kuyaBaka; 09-16-2009 at 06:07 PM.

 09-16-2009 #7 (permalink) Apple is A Games   Join Date: Oct 2007 Location: none yo business Posts: 1,412 iTrader: (0) IGN: CarmelSan Class: Eir Guild: OurStory Yeah, I got a negative too...I think the TS is missing something. T_T __________________ How sexy. <3
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Quote:
 Originally Posted by Yume x+y=100 100(.8)=x(.12)+y(.05) Uh, from what I think... the second equation should be 100(.08)=x(.12)+y(.05) to solve for x and y, take your first equation x+y=100, and rewrite it as y=100-x and then put this into your second equation so 100(.8)=x(.12)+(100-x)(.05) 8=.12x+5-.05x solve for x then when you have x, put it in for x+y=100 to figure out y if it's not this, then I don't know /o/
Yume is right.
Letting x= amt. of feed A and y = amt of feed B,

x + y=100 (1)
8= 0.12x + 0.05y (2)

From (1): y= 100 - x. (3)

Sub (3) into (2):

8 = 0.12x + 0.05(100 - x)
3 = 0.07x

x = 42.86. (4)

Sub (4) into (3)

y= 100 - 42.86 = 57.14
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Quote:
 The Word Problem is: A zookeeper needs to mix feed for the prairie dogs so that the feed has the right amount of protein. Feed A has 12% protein. Feed B has 5% protein. How many pounds of each does he need to mix to get 100 pounds of feed that is 8% protein.
Quote:
 Originally Posted by Javier Yume is right. Letting x= amt. of feed A and y = amt of feed B, x + y=100 (1) 8= 0.12x + 0.05y (2) From (1): y= 100 - x. (3) Sub (3) into (2): 8 = 0.12x + 0.05(100 - x) 3 = 0.07x x = 42.86. (4) Sub (4) into (3) y= 100 - 42.86 = 57.14

Totally skipped over that little part of the question.
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Quote:
 Originally Posted by Javier Yume is right. Letting x= amt. of feed A and y = amt of feed B, x + y=100 (1) 8= 0.12x + 0.05y (2) From (1): y= 100 - x. (3) Sub (3) into (2): 8 = 0.12x + 0.05(100 - x) 3 = 0.07x x = 42.86. (4) Sub (4) into (3) y= 100 - 42.86 = 57.14
Quote:
 Originally Posted by Yume x+y=100 100(.8)=x(.12)+y(.05) Uh, from what I think... the second equation should be 100(.08)=x(.12)+y(.05) to solve for x and y, take your first equation x+y=100, and rewrite it as y=100-x and then put this into your second equation so 100(.8)=x(.12)+(100-x)(.05) 8=.12x+5-.05x solve for x then when you have x, put it in for x+y=100 to figure out y if it's not this, then I don't know /o/
Thanks you two. Also.
Quote:
 Originally Posted by Sanichi x+y=100 100(.08)=x(.12)+y(.05)
I forgot to add the 0 when typing so I guess for those looking the word problem. . . .
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 09-16-2009 #11 (permalink) 2 kawaii 4 u Games Awards   Join Date: Jun 2008 Location: Fresno, CA Posts: 3,831 Blog Entries: 166 iTrader: (0) IGN: Euler Breslau Class: SMN-main, AST. Level: i200 SMN Guild: Get Some LLC Here's how I solved it. Complete with a scan and colored ink. __________________ Battletag: Kebbysaurus#1662 FFXIV(Midgardsormr): Euler Breslau - 60 SMN, AST, SCH, WHM, BRD, BLM, CUL, GSM, BTN, MIN, LTW, CRP, WVR tumblr? | twitter me timbers!
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Quote:
 Originally Posted by kuyaBaka Here's how I solved it. Complete with a scan and colored ink.
I believe I understand the information now.
Thanks all of you!
kuyaBaka, Yume, and Javier~

The way I have been doing these problems. . . `-`
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 09-16-2009 #13 (permalink) Lazy Lurkin' Games   Join Date: Jun 2008 Location: North Carolina/Singapore Posts: 2,242 Blog Entries: 3 iTrader: (0) IGN: Ripchord Class: Commando Ah, yes.. using the (1) +/- (2) approach to eliminate a variable also works but it's not that obvious sometimes lol. I tend to prefer substitution, can't go wrong with it :> __________________ It's the nature of my circuitry.

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