Help with a maths problem

2007-12-05 20:08:44

#1

seb--morin: Im high; +152|7077|Montréal, Québec

Hi guys, i have some exercise to do for my math course and there is a problem that really bug me! I tried some solution but i don't get any answer that seems to be right... so here it is...

A window is formed by a rectangle and a half-circle on top of it. The perimeter of the window is 9 m.Express the area (A) of the window by function of his width (x) .

So i actually have to do a function of the area to the perimeter ... F(A) = x.....

HELP PLZZZ !!! I'm not a lazy bastard that want an answer to do this easy, i actually want explanation on how to do it!

https://img98.imageshack.us/img98/2554/shitttsv1.jpg

2007-12-05 20:21:12

#2

Andoura: Got loooollllll ?; +853|7076|Montreal, Qc, Canada

Easy... 9m * x = 9x
9x + 9m = 18xm
Perimeter = 18 xm!

* I dont have any fkin idea*

2007-12-05 20:23:59

#3

Eagle: Togs8896 is my evil alter ego; +567|7068|New Hampshire, USA

Id be able to help you with algebra or calculus or triginometry even, but this was never my strong point. I hate cirlces I was all excited when I heard about Pi too. But it wasnt a pie, it was a lie!!!!

https://static.bf2s.com/files/user/14407/Sig_Pats.jpg

2007-12-05 20:26:05

#4

seb--morin: Im high; +152|7077|Montréal, Québec

-=]NS[=-Eagle wrote:
I hate cirlces I was all excited when I heard about Pi too. But it wasnt a pie, it was a lie!!!!

i lol'ed on this one! Some ppl do a lifetime work on Pi, i dont understand whats going in they're mind!

2007-12-05 20:28:46

#5

cowami: OY, BITCHTITS!; +1,106|6727|Noo Yawk, Noo Yawk

Let L=length
Let W=width
Let r=radius of circle

r = (1/2)W [Look at the diagram, it is]

9 m = 2L + W + 1/2(pi)(W)

A = LW + pi(r²)
A = LW + 1/4(pi)(W²)

Substitute W with x, and that ought to be the area. Is there supposed to be a different variable for the length, though? Doesn't work as well without one.

Last edited by cowami (2007-12-05 20:29:30)

2007-12-05 20:29:19

#6

RandomSchl: |\/|€|\/|ß€|2; +52|6881|California

well, if x is the width and y is the length...then

x * y = the area of the rectangle.

(pi * (x/2)^2) / 2 = area of semi-circle.

So those two equations added together make up the area of the whole figure.

I don't know how to express the sides of the rectangle with one variable because the length and width are different dimensions. If it was a square then you could just use x for a side. Hope that helps.

EDIT: WAIT I think this will help too... x + y = 9. y = 9 - x. Substitute this in the area equation...

x * (9 - x) = 9x - x^2 = area of rectangle.

So the final answer should be 9x - x^2 + ((pi * (x/2)^2) / 2 ) = equals area of whole thing.

Hope that helps...

EDIT AGAIN: NVM this is all wrong

Last edited by RandomSchl (2007-12-05 20:53:24)

2007-12-05 20:30:38

#7

Yellowman03: Once Again, We Meet at Last; +108|6672|Texas

ans = X((9 - X - X * PI / 2 ) / 2) + ((X / 2 )^2 * PI) / 2)

follow order of operations

pm me if you want explanation

Last edited by Yellowman03 (2007-12-05 20:43:59)

2007-12-05 20:31:24

#8

David.P: Banned; +649|6711

Fuck! If i could'nt figure this easy shit out how am i gonna fare on the SAT?

2007-12-05 20:31:34

#9

cowami: OY, BITCHTITS!; +1,106|6727|Noo Yawk, Noo Yawk

Yellowman03 wrote:
ans = X((9 - X - X * PI) / 2) + ((X^2) * PI) / 2)

pm me if you want explanation

nerd

gtfo

2007-12-05 20:33:13

#10

Yellowman03: Once Again, We Meet at Last; +108|6672|Texas

cowami wrote:
Yellowman03 wrote:
ans = X((9 - X - X * PI) / 2) + ((X^2) * PI) / 2)

pm me if you want explanation
nerd

gtfo

don't be jealous cuz i pwz teh maths

afterall...i'm asian

2007-12-05 20:33:18

#11

seb--morin: Im high; +152|7077|Montréal, Québec

Yellowman03 wrote:

ans = X((9 - X - X * PI) / 2) + ((X^2) * PI) / 2)

i dont get the 1st part....

i think that its okay like this
Y * X +( Pi (r'2)) /2

Last edited by 0seb--morin0 (2007-12-05 20:36:26)

2007-12-05 20:35:15

#12

nukchebi0: Пушкин, наше всё; +387|6761|New Haven, CT

How about:

F(A)=x.5[9-(x+1/2x(pi))]+.5(1/2x)^2(pi)

Look at the area as the rectangle and the half circle.

You know the width (x), but no the height. However, since we also know the total perimeter, we can subtract what we do know (the width and the half circle circumference) from nine to get the length of the heights added together. Dividing by 2 (.5 multiplication) give us the length of one, which we use to find the area. Finally, we add the area of the half circle, which is half of the radius (1/2x) squared times pi.

2007-12-05 20:35:49

#13

cowami: OY, BITCHTITS!; +1,106|6727|Noo Yawk, Noo Yawk

Yellowman03 wrote:
cowami wrote:
Yellowman03 wrote:
ans = X((9 - X - X * PI) / 2) + ((X^2) * PI) / 2)

pm me if you want explanation
nerd

gtfo
don't be jealous cuz i pwz teh maths

afterall...i'm asian

OMG WAT A COINCIDENCE

AZNPOWAZ

And yet, ironically, I fail at math.

2007-12-05 20:40:07

#14

Havok: Nymphomaniac Treatment Specialist; +302|7112|Florida, United States

David.P wrote:
Fuck! If i could'nt figure this easy shit out how am i gonna fare on the SAT?

I took the SAT last Saturday, and this question is way harder than any of the math on it. Trust me.

2007-12-05 20:41:58

#15

seb--morin: Im high; +152|7077|Montréal, Québec

nukchebi0 wrote:
How about:

F(A)=x.5[9-(x+1/2x(pi))]+.5(1/2x)^2(pi)

Look at the area as the rectangle and the half circle.

You know the width (x), but no the height. However, since we also know the total perimeter, we can subtract what we do know (the width and the half circle circumference) from nine to get the length of the heights added together. Dividing by 2 (.5 multiplication) give us the length of one, which we use to find the area. Finally, we add the area of the half circle, which is half of the radius (1/2x) squared times pi.

Very good, but the perimeter of 9m is WITH the half circle... the half circle is part of the window... so we have 1/2 of x*y and 1/2 of pi (r2) ....

Havok wrote:
David.P wrote:
Fuck! If i could'nt figure this easy shit out how am i gonna fare on the SAT?
I took the SAT last Saturday, and this question is way harder than any of the math on it. Trust me.

What is SAT ? Im in canada so maybe its a US thing?...

Last edited by 0seb--morin0 (2007-12-05 20:42:58)

2007-12-05 20:42:47

#16

David.P: Banned; +649|6711

Havok wrote:
David.P wrote:
Fuck! If i could'nt figure this easy shit out how am i gonna fare on the SAT?
I took the SAT last Saturday, and this question is way harder than any of the math on it. Trust me.

SAT or ACT?

2007-12-05 20:44:08

#17

Havok: Nymphomaniac Treatment Specialist; +302|7112|Florida, United States

David.P wrote:
Havok wrote:
David.P wrote:
Fuck! If i could'nt figure this easy shit out how am i gonna fare on the SAT?
I took the SAT last Saturday, and this question is way harder than any of the math on it. Trust me.
SAT or ACT?

I took SAT last Saturday and I take the ACT this Saturday.

Sux2bme

0seb--morin0 wrote:
Havok wrote:
David.P wrote:
Fuck! If i could'nt figure this easy shit out how am i gonna fare on the SAT?
I took the SAT last Saturday, and this question is way harder than any of the math on it. Trust me.
What is SAT ? Im in canada so maybe its a US thing?...

It's the nationwide standardized test for applying to college. Most colleges accept the SAT and a few the ACT.

Last edited by Havok (2007-12-05 20:46:37)

2007-12-05 20:47:49

#18

David.P: Banned; +649|6711

Lucky fuck you are havok! I cant take it yet because i cant afford too and i dont wanna ask my parents fro money since i'm 19 already! Shit i gotta move on with my life!

2007-12-05 20:50:47

#19

nukchebi0: Пушкин, наше всё; +387|6761|New Haven, CT

0seb--morin0 wrote:
Very good, but the perimeter of 9m is WITH the half circle... the half circle is part of the window... so we have 1/2 of x*y and 1/2 of pi (r2) ....

Duh. I accounted for that. You don't have half of x*y, you have the whole x*y plus 1/2 of the circle. You are adding a rectangle to a half circle.

2007-12-05 20:57:41

#20

nukchebi0: Пушкин, наше всё; +387|6761|New Haven, CT

https://img338.imageshack.us/img338/2720/drawinghu7.jpg

There. Illustrated for you because I can't explain well.

Last edited by nukchebi0 (2007-12-05 20:58:10)

2007-12-05 21:15:26

#21

DrunkFace: Germans did 911; +427|7118|Disaster Free Zone

Semicircle:
radius = ½x
Circumference = (½*2)PI(r) = ½PI(x)
Area = ½(PI)(r²)
= 0.125PI(x²)

Rectangle:
base = x
height = ½(9 - x - ½PI(x))
Area = b * h
= 4.5(x) - ½x² - ¼PI(x²)

.: Area = Rectangle + Semicircle
= 4.5(x) - ½x² - 0.125PI(x²)

Last edited by DrunkFace (2007-12-05 21:17:41)

2007-12-05 21:25:21

#22

nukchebi0: Пушкин, наше всё; +387|6761|New Haven, CT

Thanks for simplifying it for me.

2007-12-05 21:31:03

#23

seb--morin: Im high; +152|7077|Montréal, Québec

thks a lot guys for your help! I got graph to do now!! If i can figure out to use properly my Ti 83 i should be easy !

2007-12-06 03:57:56

#24

unnamednewbie13: Moderator; +2,072|7209|PNW

0seb--morin0 wrote:
Hi guys, i have some exercise to do for my math course and there is a problem that really bug me! I tried some solution but i don't get any answer that seems to be right... so here it is...

A window is formed by a rectangle and a half-circle on top of it. The perimeter of the window is 9 m.Express the area (A) of the window by function of his width (x) .

So i actually have to do a function of the area to the perimeter ... F(A) = x.....

HELP PLZZZ !!! I'm not a lazy bastard that want an answer to do this easy, i actually want explanation on how to do it!

http://img98.imageshack.us/img98/2554/shitttsv1.jpg

The question doesn't take into account the thickness or number of panes (I suppose it doesn't care about edges and two sides ) or how deep into the frame they may sit, or if the latter is irrelevant, how crooked the frame may be, or if the walls have settled on any axis, thus altering the viewable shape.

-=]NS[=-Eagle wrote:
Id be able to help you with algebra or calculus or triginometry even, but this was never my strong point. I hate cirlces I was all excited when I heard about Pi too. But it wasnt a pie, it was a lie!!!!

The pi is a lie.
The pi is a lie.
The pi is a lie.
The pi is a lie.

Last edited by unnamednewbie13 (2007-12-06 04:02:49)

2007-12-06 04:15:17

#25

DrunkFace: Germans did 911; +427|7118|Disaster Free Zone

unnamednewbie13 wrote:
The question doesn't take into account the thickness or number of panes (I suppose it doesn't care about edges and two sides ) or how deep into the frame they may sit, or if the latter is irrelevant, how crooked the frame may be, or if the walls have settled on any axis, thus altering the viewable shape.

lol, It's like a year 10 maths problem to teach you to break hard problems down into smaller more manageable parts, not an engineering degree, give them time and they'll see how pitifully easy this question really is.

BF2S Forums Help with a maths problem

-=]NS[=-Eagle wrote:

Yellowman03 wrote:

cowami wrote:

Yellowman03 wrote:

Yellowman03 wrote:

cowami wrote:

Yellowman03 wrote:

David.P wrote:

nukchebi0 wrote:

Havok wrote:

David.P wrote:

Havok wrote:

David.P wrote:

David.P wrote:

Havok wrote:

David.P wrote:

0seb--morin0 wrote:

Havok wrote:

David.P wrote:

0seb--morin0 wrote:

0seb--morin0 wrote:

-=]NS[=-Eagle wrote:

unnamednewbie13 wrote:

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