IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: cashem'up on September 09, 2009, 04:59:51 pm

Title: maxima.......question...very tough
Post by: cashem'up on September 09, 2009, 04:59:51 pm
hey guys very long question...neone has P1 pg110 q16....very hard...just see if u can answer Thanks
Title: Re: maxima.......question...very tough
Post by: Ghost Of Highbury on September 09, 2009, 05:01:16 pm
Quote from: ima_shah2002 on September 09, 2009, 04:59:51 pm
hey guys very long question...neone has P1 pg110 q16....very hard...just see if u can answer Thanks
which book??

which subject?/

plzz post ur question so that some1 can help u out
 :)
Title: Re: maxima.......question...very tough
Post by: nid404 on September 09, 2009, 05:03:48 pm
Is it the cylinder ans sphere question...i'll answer it after im back from dinner
or post the question..not too big..som1 else can answer it in the meantime
Title: Re: maxima.......question...very tough
Post by: cashem'up on September 09, 2009, 05:47:44 pm
yep that question....its

1. a circular cylinder is to fit inside a sphere of radiius 10cm. Calculate the maximum possible volume of the cylinder(probably best to take height of cylinder as your independent variable).
Title: Re: maxima.......question...very tough
Post by: nid404 on September 09, 2009, 06:23:33 pm
I'm not getting it right unfortunately but I'll keep trying...I've gone wrong somewhere but can't figure out
Title: Re: maxima.......question...very tough
Post by: cashem'up on September 09, 2009, 06:42:13 pm
yeah it seems to be a tricky question......letz wait for astar........
Title: Re: maxima.......question...very tough
Post by: nid404 on September 09, 2009, 06:50:43 pm
I guess that's what we should do...I managed to find the radius of the cylicnder as 6.67cm...but my finally answer is wrong
Title: Re: maxima.......question...very tough
Post by: astarmathsandphysics on September 09, 2009, 06:56:48 pm
The answer is in the attached doc. I am messing about with openoffice trying to create webpages now.
Title: Re: maxima.......question...very tough
Post by: nid404 on September 09, 2009, 07:12:29 pm
oh that was that....i simply went into crap..
Thanks sir :)
Title: Re: maxima.......question...very tough
Post by: cashem'up on September 10, 2009, 05:53:21 pm
hey astar.....the answer is not comin rite m gettin 855cm3 but the actual answer is 2420cm3

Title: Re: maxima.......question...very tough
Post by: astarmathsandphysics on September 10, 2009, 06:47:17 pm
Did you download the pdf I posted earlier in this thread? What did you get for tanx?
Title: Re: maxima.......question...very tough
Post by: cashem'up on September 10, 2009, 07:00:48 pm
tanx= 0.707
and  x=35.26
then i substituted in orig.. eqn for VOl
Title: Re: maxima.......question...very tough
Post by: astarmathsandphysics on September 10, 2009, 07:01:58 pm
r=10 for the sphere butthe radius of the cynder is 2rsinx =2*10*1/sqrt5=8.94 and height is 2rcosx=20*2/sqrt5=17.9 so volume=3.14*8.95^2*17.9=4489
Title: Re: maxima.......question...very tough
Post by: astarmathsandphysics on September 10, 2009, 07:03:56 pm
The formula for the volume is wrong. I should have included a factor 8 cos I only had half the height and half the volume. Also there are 2 x's in the diagram but there should only be one, at the edge of the circle.
Title: Re: maxima.......question...very tough
Post by: cashem'up on September 12, 2009, 05:19:15 am
yes i can understand but the actual given answer is 2420.....
Title: Re: maxima.......question...very tough
Post by: nid404 on September 12, 2009, 06:21:21 am
When I solved it
i got h=5.77x2
=11.547
r=8.165
v=pir2h
=2417.19...which is 2420 to three significant figures