Math Is Fun Forum

xiukhung

Guest

Spheres problem

4 spheres are placed on a table so that each touches 2 others and their centres form a square. Another sphere is placed on top. Find the height of the top of the fifth sphere above the table.

dnsd

Guest

Re: Spheres problem

(root2 +1)r

ZHero

Real Member

Registered: 2008-06-08

Posts: 1,889

Re: Spheres problem

My answer is 3.5r

I guess that the 5 points will form a Pyramid with Square Base and Each Side of length 2r.
Height of the 5th point from the Base =1.5r and thus heigh of Sphere from table = 3.5r

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If two or more thoughts intersect, there has to be a point!

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Spheres problem

Height of the 5th point from the Base =1.5r

No, no, it is (√2)r.

xiukhung

Guest

Re: Spheres problem

Thanks a lot, what about this problem?
A sphere of radius length 8cm rests on top of a hollow inverted cone of height 15 cm whose vertical angle is 60 degrees. Find the height of the centre of the sphere above the vertex of the cone.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Spheres problem

Hi xiukhung;

Whoa, there are 4 different answers, which did you like best? Do you already know the answer?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

xiukhung

Guest

Re: Spheres problem

Hi xiukhung;

Whoa, there are 4 different answers, which did you like best? Do you already know the answer?

Idk cuz i have the answer at the back of my book, which is 34.14cm, and i forgot to say that the radius of 1 sphere is 10cm.

ZHero

Real Member

Registered: 2008-06-08

Posts: 1,889

Re: Spheres problem

Height of the 5th point from the Base =1.5r

No, no, it is (√2)r.

Oh ya... I got it Now!!
Am just another boob sometimes!!

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If two or more thoughts intersect, there has to be a point!