View Full Version : Who's good at math?

Dommzyd

03-04-2009, 04:40 PM

This is one of the practice questions on my stupid 200 question military test I'm studying for.

What is the distance covered in one revolution of a wheel whose diameter is 21 inches? Use pi = 22/7.

So... The distance covered would be the circumference, correct?

C = pi(21) ?

I forgot the stupid circumference formula, but I think it's C = pi(diameter)

I need to do it from the diameter, not the radius.

Which would make the circumference 66. Am i right o_O

pi x 21 = 22/7 x 21 = 22/1 x 3/1 = 66

RIGHT?

If I'm doing it wrong, tell me cuz I really need to know how to do these problems, lol.

Merde

03-04-2009, 04:42 PM

Circumference is Pi(R2) I believe. Either that or 2Pi(R). Get them mixed up. I do believe it's the first one though

MissKristenHXC

03-04-2009, 04:43 PM

C=pir2 [pi r(radius)2(squared)]

Hope that helped

Dommzyd

03-04-2009, 04:43 PM

Circumference is Pi(R2) I believe. Either that or 2Pi(R). Get them mixed up. I do believe it's the first one though

Well yea but 2r is d.

If your radius is 3, the diameter is 6.

C=pir2

Hope that helped

Same thing as C = pi(d)

Teddybear

03-04-2009, 04:44 PM

Circumferance of a Circle = 2(PI)R

Diameter/2 = Radius = 21/2

2(22/7)(21/2)=66

Teddybear

03-04-2009, 04:44 PM

c=pir2 [pi r(radius)2(squared)]

hope that helped

Fail. That is the area.

Merde

03-04-2009, 04:44 PM

Well yea but 2r is d.

If your radius is 3, the diameter is 6.

Woops, meant Pi(r)squared. Square the radius and multiply by 22/7

Dommzyd

03-04-2009, 04:46 PM

Woops, meant Pi(r)squared. Square the radius and multiply by 22/7

It tells me to find the circumference from the diameter though, not from the radius. So I would be using C = pi(d) instead of the radius formula.

I know the answer is 66, it says it in the answers part... It just doesn't tell me how to get there.

Merde

03-04-2009, 04:48 PM

It tells me to find the circumference from the diameter though, not from the radius. So I would be using C = pi(d) instead of the radius formula.

I know the answer is 66, it says it in the answers part... It just doesn't tell me how to get there.

Lol, you take half of the diameter to find the radius xD

21/2= 10.5

10.5(squared)= 110.25

Pi(110.25) = 346.185

. . .

Yeah, it's C=2piR (Pi(r)x2)

Dommzyd

03-04-2009, 05:04 PM

Lol, you take half of the diameter to find the radius xD

21/2= 10.5

10.5(squared)= 110.25

Pi(110.25) = 346.185

. . .

Yeah, it's C=2piR (Pi(r)x2)

I know you take half the diameter to find the radius, but there's 2 different formulas.

The one you just used is wrong. The answer is 66, I just don't know exactly how to get it. I think my original answer was right, but I'm not 100%

Teddybear

03-04-2009, 07:35 PM

Did you even look at my answer Dommzy!

Dommzyd

03-04-2009, 07:39 PM

Did you even look at my answer Dommzy!

Yes! I have to do it by the diameter formula though, not the radius.

It's stupid, I know.. but that's what it says in the book :/.

Pyros

03-05-2009, 04:47 AM

Yes! I have to do it by the diameter formula though, not the radius.

It's stupid, I know.. but that's what it says in the book :/.

>.> you could just subsitute the radius for the diameter though.

C = 2(pi)R

but R = D/2 strangely enough that means that

C = 2(pi)(D/2)

which pretty much turns into

C = (pi)D

which is LAME. but is the answer you really need.

3.14*21 = 65.94 or something aka 66. and FYI 22/7 is NOT pi >.>

Pyros

Dommzyd

03-05-2009, 06:46 AM

>.> you could just subsitute the radius for the diameter though.

C = 2(pi)R

but R = D/2 strangely enough that means that

C = 2(pi)(D/2)

which pretty much turns into

C = (pi)D

which is LAME. but is the answer you really need.

3.14*21 = 65.94 or something aka 66. and FYI 22/7 is NOT pi >.>

Pyros

So I was right.... PYROS READ! Lmao.

Dommzyd

03-05-2009, 06:47 AM

>.> you could just subsitute the radius for the diameter though.

C = 2(pi)R

but R = D/2 strangely enough that means that

C = 2(pi)(D/2)

which pretty much turns into

C = (pi)D

which is LAME. but is the answer you really need.

3.14*21 = 65.94 or something aka 66. and FYI 22/7 is NOT pi >.>

Pyros

This is one of the practice questions on my stupid 200 question military test I'm studying for.

What is the distance covered in one revolution of a wheel whose diameter is 21 inches? Use pi = 22/7.

Get it together, Pyros. The problem says to use 22/7 = pi.

I know what pi is, lol.

Pyros

03-05-2009, 06:49 AM

So I was right.... PYROS READ! Lmao.

Get it together, Pyros. The problem says to use 22/7 = pi.

I know what pi is, lol.

O_o yes you are right.

and I fail at reading ><

Pyros

Dommzyd

03-05-2009, 06:49 AM

O_o yes you are right.

and I fail at reading ><

Pyros

Lmao, it's okay.

So did I do the problem right o_O

Pyros

03-05-2009, 06:51 AM

Lmao, it's okay.

So did I do the problem right o_O

Just to confirm. Yes you did

Pyros

Dommzyd

03-05-2009, 06:51 AM

Just to confirm. Yes you did

Pyros

Yessss +1 for me.

Matt_hew86

03-05-2009, 08:23 AM

You had it right first time....

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