PDA

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
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.

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

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

Teddybear
03-04-2009, 04:44 PM
hope that helped

Fail. That is the area.

Merde
03-04-2009, 04:44 PM
Well yea but 2r is d.
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....