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Homework Help

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eldeablo666
Post #523531 - Reply to (#523513) by Cherelle Ashlee
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12:49 am, Feb 16 2012
Posts: 27


Quote from Cherelle Ashlee
Can anyone help me with this math equation please!! This is my last question but I cant seem to get it ( This is system of equations)


At the beginning of a new semester, Andy makes plans for a successful semester. He allocates 42 hours per week for study time for the four courses he is taking: Math English, Chemistry and History. He decides to allocate half of his time to Math and English, and two as much time to Math as to English. He decides to allocate twice as much to English as to History.

a) find a sytem of equations that represents this information.
b) solve the system to determine the number of hours allocated to each subject.

Can anyone help please!!

ok if im right we did this recently and if i remember you would do something like
21=2e+e
variables:
2e=math
e=english
1/2e=history
42=2x+x+1/2x+c
this should solve this one
x= first equations value for e
c= value for chem
21=2e+e >> 21/3=e >> e=7 hr
so history should be 4 hr
math 16hr
english 8hr
42=3.5+14+7+c
42-24.5=24.5-24.5+c
17.5=c
there for your answer is chem=17.5, english=7, math=14, history=3.5
this is at least how i was taught where i live last year biggrin

Cherelle Ashlee
Post #523539 - Reply to (#523525) by StarlightDreams
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Shoujo Queen
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1:33 am, Feb 16 2012
Posts: 402


Quote from StarlightDreams
Quote from Cherelle Ashlee
Can anyone help me with this math equation please!! This is my last question but I cant seem to get it ( This is system of equations)


At the beginning of a new semester, Andy makes plans for a successful semester. He allocates 42 hours per week for study time for the four courses he is taking: Math English, Chemistry and History. He decides to allocate half of his time to Math and English, and two as much time to Math as to English. He decides to allocate twice as much to English as to History.

a) find a sytem of equations that represents this information.
b) solve the system to determine the number of hours allocated to each subject.

Can anyone help please!!


Make variables for each subject. M = Math, E = English, C = Chem, H = History

21 = M + E <- It says he allocated half of the time to math and english.
M = 2E <- It says that that he allocates twice as much time to math as to english
E = 2H <- allocates twice as much to English as to history
M + E + C + H = 42

Start with the first two equations.
21 = M + E and M = 2E
Do the system of equations for those two variables. Once you do that, plug in whatever you got for E into the third equation and solve for H. Now you have 3/4 variables found and can find C by adding M, E, and H together and subtracting it from 42.



@StarlightDreams Thank you soooo much for your help, I just solve it by your help

@eldeablo666 thanks for your help also!! Your answers confirm that I wrote my equation right! Thanks!!!

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MewMan
Post #523548 - Reply to (#523507) by StarlightDreams
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hmm~
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2:51 am, Feb 16 2012
Posts: 933


Quote from StarlightDreams
The negative equivalent of pi/3 isn't one of the points? -5pi/3?


it is
that's why I used "sets of points" instead of just "points"
too lazy to write t=-pi/3+2*k*pi (k=integer) XD

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Sagaris
Post #523552 - Reply to (#523469) by MewMan
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3:10 am, Feb 16 2012
Posts: 3116


Quote from MewMan
Can someone tell me how to find the exact points, instead of just the angles?

It's a circle...

x=rcos(theta)
y=rsin(theta)

MewMan
Post #523556
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hmm~
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3:44 am, Feb 16 2012
Posts: 933


^I don't think I get what you're trying to say T_T
converting polar functions into rectangular ones before solving, maybe?

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Sagaris
Post #523562
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4:05 am, Feb 16 2012
Posts: 3116


Wait... you want the points in polar coordinates?

But... that's just the radius and the angle.

MewMan
Post #523600 - Reply to (#523562) by Sagaris
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hmm~
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7:04 am, Feb 16 2012
Posts: 933


Quote from Sagaris
Wait... you want the points in polar coordinates?

But... that's just the radius and the angle.

uhm...
you have a point there XD
guess I will rest the case here
wasted too much time already dead


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yokeepsitreal
Post #523850
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5:18 pm, Feb 17 2012
Posts: 158


need ap calc help its a definite integral problem

its the one where there is a long "s" at the beginning of the equation



4
S 5/x (the 5/x is all in a radical sign)
1


MewMan
Post #523854
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hmm~
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5:53 pm, Feb 17 2012
Posts: 933


(ln(x))' = 1/x
there you go sir biggrin


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jelzin89
Post #523855 - Reply to (#523850) by yokeepsitreal
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5:56 pm, Feb 17 2012
Posts: 270


Quote from yokeepsitreal
need ap calc help its a definite integral problem

its the one where there is a long "s" at the beginning of the equation



4
S 5/x (the 5/x is all in a radical sign)
1


if I read this right you want to integrate the function 5/x over the interval [1,4].and where is the problem?
build the stem-function and just ingerate it.since the interval is [1,4] you don't have to watch out for the symmetry of the graph.
the stem-function to 1/x = ln(x)

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Cherelle Ashlee
Post #541308
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Shoujo Queen
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11:51 pm, Mar 21 2012
Posts: 402


Can anyone help me with this equation. This is venn diagram survey problems, but I can't solve it!

A survey is made of people, all of whom enjoy at least one of the activities music, painting and sculpture.

34% enjoys painting
18% enjoy both sculpture and painting
16% both sculpture and music
9% sculpture only
24% both painting and music
Twice as many enjoy painting as enjoy sculpture

Let n(FnGnL)=x
Draw a venn diagram and mark on it, in terms of x where neceesary the number of students represented by each region
Form an equation in x and solve it.

What percentage enjoy:
a) all three
b) just one of the three?

Can anybody please help me!! (i have been trying for the past 2 nights to find m=music sad )

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Seijurou
Post #541314 - Reply to (#541308) by Cherelle Ashlee
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1:01 am, Mar 22 2012
Posts: 597


Quote from Cherelle Ashlee
Can anyone help me with this equation. This is venn diagram survey problems, but I can't solve it!

A survey is made of people, all of whom enjoy at least one of the activities music, painting and sculpture.

34% enjoys painting
18% enjoy both sculpture and painting
16% both sculpture and music
9% sculpture only
24% both painting and music
Twice as many enjoy painting as enjoy sculpture

Let n(FnGnL)=x
Draw a venn diagram and mark on it, in terms of x where neceesary the number of students represented by each region
Form an equation in x and solve it.

What percentage enjoy:
a) all three
b) just one of the three?

Can anybody please help me!! (i have been trying for the past 2 nights to find m=music sad )


Correct me if I'm wrong, but do those numbers not add up to 101%?

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QuasarX
Post #541325
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1:35 am, Mar 22 2012
Posts: 169


I choose these variables:

m = likes music only
p = likes painting only
s = likes sculpture only
x = likes music and painting, but not sculpture
y = likes music and sculpture, but not painting
z = likes painting and sculpture, but not music
a = likes all three

Then, I represent the given statements with the following equations:

p + x + z + a = 34
z + a = 18
y + a = 16
s = 9
x + a = 24
p + x + z + a = 2 * (s + y + z + a)

I then begin simplifying the equations, starting with the last one:

p + x + z + a = 2 * (s + y + z + a)
34 = 2 * (s + y + z + a) {substitute using 1st equation}
17 = s + y + z + a {divide both sides by 2}
17 = 9 + y + z + a {substitute using 4th equation}
8 = y + z + a {subtract 9 from both sides}
8 = y + 18 {substitute using 2nd equation}
-10 = y {subtract 18 from both sides}

Since, by definition, percentages must fall within the range 0..100 inclusive, y cannot be -10, thus proving the 6 given statements, as written, to be in contradiction. There is no solution. Q.E.D.

red255
Post #541328 - Reply to (#541314) by Seijurou
Member

1:56 am, Mar 22 2012
Posts: 215


Quote from Seijurou
Correct me if I'm wrong, but do those numbers not add up to 101%?


thats the point.

the % contain overlap, so they should add up to 101+X% and that X% is well, your solution to the problem

So we got a Venn Diagram with 3 circles.
Painting Circle
Sculpture Circle
Music Circle.

I can't draw very well Here. but its got 7 parts that add up to 100%.

To find music, we look, Painting (34%) I assume includes P+PM+PS+X.

so 34+9 (sculpture only) is going to leave Music only and MS which is 16 %.

so whats left is 100-34-9 = 41% music only.

Course looking at the TWICE AS MANY PEOPLE ENJOY Painting as sculture, that would make the total for sculture 34/2 = 17 which is wrong.

so yeah, 34 is painting only. Blah... looks. those aren't %. those are people polled.

34 PEOPLE like painting only, out of like 150 people.

So anyways. we got for painting 34 + 18 +24 +X = 2(Sculpture) which is 9+18+16+X right?

so 76+X = 86 + 2X

Er... X would be -10 people.....

yeah the numbers aren't working. but if they were working I guess -10% for X and 9 for music only would solve the diagram, its just not a valid answer.



Cherelle Ashlee
Post #541350 - Reply to (#541328) by red255
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Shoujo Queen
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4:05 am, Mar 22 2012
Posts: 402


I have gotten -10 in class to but that cannot be the answer, we asked him and he told us that there is no mistakes in that equations.

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