C2 Differentiation Question Help

The entire surface area of the tin 80π=2πx² + 2πx + 2πxh

The Volume of the tin V=πx²h

h is unknown in both equations.. therefore... rearranging 2nd equation we get

V/πx²=h.....then substitute this into the very first equation to get

80π=2πx² + 2πx + 2πxV/πx²
Tidy up yada yada yada...etc....

40πx²-πx²-πx³=V
Factorising...

V = π(40x - x2 - x3)

Reply 2

__WiZaRD__

OP

2

yea, i was really close, why did you get + 2πx for the first step?

Reply 3

2πx is the surface area of the overlapping part of the lid....

Reply 4

steve2005

17

super_baros

2?x is the surface area of the overlapping part of the lid....

I have not read the whole post but 2?x appears to have dimensions of length and not area.

Reply 5

Come on guys it's xmas!
Leave maths for another day. :cool:

Reply 6

2πx is the surface area of the overlapping part of the lid....

The radius is x....c = πd
d = 2x.... therefore c = 2πx... the overlapping part of the lid is only 1cm... so therefore.. it is 2πx X 1 = 2πx

Reply 7

__WiZaRD__

OP

2

yea, i get it, thx, and a merry christmas to you all :smile:

Reply 8

__WiZaRD__

yea, i get it, thx, and a merry christmas to you all :smile:

Good...good... Merry christmas....

Reply 9

El Stevo

11

Widowmaker

Come on guys it's xmas!
Leave maths for another day. :cool:

http://www.thestudentroom.co.uk/showthread.php?p=3814851#post3814851
http://www.thestudentroom.co.uk/showthread.php?p=3814544#post3814544
http://www.thestudentroom.co.uk/showthread.php?p=3814514#post3814514
http://www.thestudentroom.co.uk/showthread.php?p=3814246#post3814246

love the one rule for them, other rule for you mr widowmaker :biggrin:

Reply 10

El Chueco

http://www.thestudentroom.co.uk/showthread.php?p=3814851#post3814851
http://www.thestudentroom.co.uk/showthread.php?p=3814544#post3814544
http://www.thestudentroom.co.uk/showthread.php?p=3814514#post3814514
http://www.thestudentroom.co.uk/showthread.php?p=3814246#post3814246

love the one rule for them, other rule for you mr widowmaker :biggrin:

Okay you've found me out. Just a bit of fun!

Reply 11

RichE

15

Widowmaker

Okay you've found me out. Just a bit of fun!

You neg rep people for fun? :confused:

Reply 12

RichE

You neg rep people for fun? :confused:

Yeah why not?
It's a stupid system anyway and most people abuse it.

Reply 13

El Stevo

11

RichE

You neg rep people for fun? :confused:

Holdup Widowmaker, you negged Rich for doing what you did? Weird. I just thought twas mere banter on your behalf..

Reply 14

El Chueco

Holdup Widowmaker, you negged Rich for doing what you did? Weird. I just thought twas mere banter on your behalf..

Yh well I've been neg repped too.
It's all square. :p:

Reply 15

RichE

15

Widowmaker

Yh well I've been neg repped too.
It's all square. :p:

Not by me you haven't - I'll have to wait till tomorrow to abuse the system. :frown:

Reply 16

El Stevo

11

Widowmaker

Yh well I've been neg repped too.
It's all square. :p:

surely it would have been simpler to just not bother negging him? its christmas after all. spread goodwill, not dish out neg rep. or something. i still cant believe you negged someone over helping someone else, especially as thats what folks do on a student website...

Reply 17