*Area of the base equals*
a)8 pi square units
b)16 pi square units
c) 64 pi square units

- anonymous

*Area of the base equals*
a)8 pi square units
b)16 pi square units
c) 64 pi square units

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- anonymous

https://suwannee.owschools.com/media/g_geo_2013/8/group100.gif

- anonymous

@jordanwhitehead

- anonymous

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## More answers

- anonymous

@UsukiDoll

- anonymous

@math1234

- UsukiDoll

I'm juggling one question back in forth.. so if I'm slow to reply sorry in advanced. Anyway we are given a cylinder |dw:1435669876398:dw|

- anonymous

It's okay

- UsukiDoll

the formula for area of the base of a cylinder is A = pi(r^2)

- anonymous

Okay. But every time I put it into the calculator it shows: either 39.4384 or 50.24

- UsukiDoll

I know.. we don't calculate the pi part.. leave it as is. so if r = 4 what is r^2?

- UsukiDoll

looking at the choices... I think it doesn't want you to calculate the pi.. it's just finding the r and then squaring it

- anonymous

Well then it's just 16

- anonymous

So it's B?

- UsukiDoll

A=pi(4^2)
A=pi(16) =16 pi
yeah

- anonymous

Thanks. So would it be about the same thing for this problem?

- anonymous

A cylinder has a volume of 245 pi cubic units and a height of 5 units. The diameter of the cylinder is
a) 7 units
b) 14 units
c) 49 units

- UsukiDoll

I think we need the diameter of the cylinder formula.

- UsukiDoll

yeah we need a different formula for that.

- UsukiDoll

\[\large V = \pi r^2h\]

- UsukiDoll

so given height is 5 units
volume is 245 pi cubic units . Looks like we're solve for r
and then the diameter is twice the radius (d=2r) .. AHA! We need to find the radius first

- anonymous

Yes

- UsukiDoll

ok let V = 245, and h = 5

- anonymous

V r h = � or 2
=

- anonymous

Well that didn't come out right

- anonymous

:(

- UsukiDoll

\[\large 245 = \pi r^2(5)\]

- anonymous

What's "large"?

- UsukiDoll

that's to make the font large

- UsukiDoll

oh are you trying to use the equation tool?
right click show math as -> tex command and it will have this code or text you can copy and paste. And then click on the equation tool and paste.

- anonymous

Oh

- UsukiDoll

so we are solving for r that would mean that r needs to be by itself

- UsukiDoll

our first goal is to have r^2 by itself .. and then afterwards we can take the square root

- anonymous

\[V = \pi r2h\]

- anonymous

r is squared

- UsukiDoll

yeah it should have that ^ that carrot sign

- UsukiDoll

\[\large V = \pi r^2h \]

- UsukiDoll

anyway back to this \[\large 245 = \pi r^2(5) \] we need r^2 by itself so what do we need to do?

- UsukiDoll

should we add both sides? subtract both sides? multiply both sides? or.. divide both sides by 5pi

- anonymous

divide both sides by 5 pi

- UsukiDoll

yes. \[\large \frac{245}{5 \pi} = r^2\]

- UsukiDoll

now we take the square root of both sides

- anonymous

So 49 = ?

- anonymous

Umm

- UsukiDoll

we're not done.. we need to take the square root on both sides

- UsukiDoll

UH OH! I need to refresh my screen is crazy

- anonymous

kk

- anonymous

Go ahead

- anonymous

I neded to digest a little

- UsukiDoll

ok so taking the square root of both sides \[\large \sqrt{ \frac{245}{5 \pi} }= \sqrt{r^2}\]
what is the square root of r^2

- UsukiDoll

we need to take the square root of r^2 so we can have r

- UsukiDoll

then once we have our r we can get the diameter. which is d =2r

- anonymous

r=2.5

- UsukiDoll

that's not a choice for answers that would've yielded d = 5.. that's not right

- anonymous

No wait. 5 was the height not the diameter

- anonymous

mY BAD SRY

- UsukiDoll

wait a minute we are solving for r.

- UsukiDoll

we have already plugged in V and h... now we need to take the square root of both sides. We're almost there

- anonymous

I was thinking that the diameter is 7

- anonymous

cus 7 squared is 49

- UsukiDoll

\[\large \sqrt{ \frac{245}{5 \pi} }= \sqrt{r^2} \]
becomes
???
what is the square root of r^2

- anonymous

49 times 3.14 = 153.86

- anonymous

Umm

- anonymous

7

- UsukiDoll

once we find r
we can find the diameter which is d = 2r

- UsukiDoll

What? ok no substituting we are solving for r we need the square root of r^2 .

- UsukiDoll

I want an r by itself

- UsukiDoll

we have square rooted both sides.. which is correct. Now we just need the square root of r^2
Then we have this \[\[\[\large \sqrt{ \frac{245}{5 \pi} }= r\] \]

- UsukiDoll

now the diameter is d=2r
so d = 2( That whole square root)

- UsukiDoll

\[\large \sqrt{r^2} \rightarrow r^{\frac{2}{2}} \rightarrow r^1 \rightarrow r \]

- UsukiDoll

so now our \[d=2(\sqrt{\frac{245}{5 \pi}})\]

- UsukiDoll

so we just need 245 divided by 5 pi... take the square root of that result and multiply by 2

- anonymous

7.9

- UsukiDoll

yes. so our diameter is 7.9 kind of a dangerous number because we can round up to 8

- UsukiDoll

7 units would be the closest to the answer.. though the real answer is 7.9

- anonymous

Okay. Look I'm sorry if I aggravated you. It's been a long couple of weeks and I'm really tired

- anonymous

Thanks for the help. I really appreciate it

- UsukiDoll

it's ok ... I'm also tired.. in fact it's almost 4 in the morning. I need zzz's before my dad get suspicious again.

- UsukiDoll

that's why I had my latex wrong... r to the first power is just r
if it was r^0 that would've been 1. But I should always take the advice of never do math while tired.

- anonymous

Yeah I can connect with that

- UsukiDoll

I have to go sleep. night

- anonymous

Really. Wow it's 9:55 AM here

- anonymous

well alright

- anonymous

I live in Florida btw

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