Math Is Fun Forum

soha

Real Member

Registered: 2006-07-07

Posts: 2,530

MensuraTION

A cylinder of height 35cm is completely filled with 11 litres of milk. Calculate its diameter.

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"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: MensuraTION

Hi soha;

11 liters = 11000 cubic centimeters

V = π r^2 h

11000 = 35 * π * r^2

So:

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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.

soha

Real Member

Registered: 2006-07-07

Posts: 2,530

Re: MensuraTION

I got
d= 20 ..

I did'nt get that pi
is that correct???

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"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: MensuraTION

Hi soha;

Let me see what you have done.

---

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.

soha

Real Member

Registered: 2006-07-07

Posts: 2,530

Re: MensuraTION

I used v= pi r^2 h
11000=22/7 × r^2 × 35
r^2=11000/35 × 7/22
r^2= root 100
r=10

if r=10 d=2r
d=20

Am i wrong?

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"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: MensuraTION

Hi soha;

It is because you used 22 / 7 for pi, remember that is only an approximation of pi.

That is the exact answer.

---

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.

soha

Real Member

Registered: 2006-07-07

Posts: 2,530

Re: MensuraTION

So 22/7 cant be used for pi any where???

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"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: MensuraTION

Hi soha;

Sure it can be used, but just as an approximation, that is why you got 10 and I got 10.004...

---

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.

soha

Real Member

Registered: 2006-07-07

Posts: 2,530

Re: MensuraTION

ok...

So here we can use 22/7 , but that is not the exact answer?

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"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: MensuraTION

No, it is not exact but it is close. 22 / 7 is a rounded off version of pi.

---

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.

soha

Real Member

Registered: 2006-07-07

Posts: 2,530

Re: MensuraTION

All right!!!

Thanks for explaining it to me

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"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"
- David O. McKay

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: MensuraTION

Hi soha;

Glad to help.

---

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.