if the radius of the cylinder is 661.9 inches cubed and the diameter is 7 inches what is the height of the cylinder to the nearest tenth of an inch?

Question

if the radius of the cylinder is 661.9 inches cubed and the  diameter is 7 inches what is the height of the cylinder to the nearest tenth of an inch?

anonymous · Answer

why is the radius in inches cubed?

anonymous · Answer

perhaps you mean the volume

anonymous · Answer

also how could the diameter be less then the radius?

jim_thompson5910 · Answer

the diameter is 7 inches, so the radius is exactly half of that: 7/2 =3.5 inches

jim_thompson5910 · Answer

assuming you meant to say the volume was 661.9 cubic inches, this would mean that

V = pi*r^2*h

661.9 = pi*(3.5)^2*h

661.9 = pi*12.25*h

661.9/(pi*12.25) = h

h = 661.9/(pi*12.25)

h = ???

anonymous · Answer

maybe i typed it wrong, heres what it looks like and im suppose to find it to the nearest tenth of an inch..

jim_thompson5910 · Answer

oh the radius is 7, not the diameter

thanks for the pic

jim_thompson5910 · Answer

V = pi*r^2*h 

661.9 = pi*(7)^2*h

661.9 = pi*49*h

661.9/(pi*49) = h

h = 661.9/(pi*49)

h = ??

jim_thompson5910 · Answer

essentially what's going on is that we're using the volume of a cylinder formula, which is V = pi*r^2*h, plugging in the given info and solving for h

anonymous · Answer

hmmm I think understand it more now, thank you!

jim_thompson5910 · Answer

so what do you get for h?

anonymous · Answer

I still didn't get it.

jim_thompson5910 · Answer

where are you stuck? which line of my steps above doesn't make sense?

anonymous · Answer

im trying to figure out what to plug in for the formula haha

jim_thompson5910 · Answer

the given volume is 661.9

so V = 661.9

jim_thompson5910 · Answer

the radius is 7, so r = 7

jim_thompson5910 · Answer

that explains line 2 in my work, making sense so far?

anonymous · Answer

somewhat

jim_thompson5910 · Answer

to get line 3, i squared 7 to get 49

anonymous · Answer

I see

jim_thompson5910 · Answer

line 4, i divided both sides by pi*49 to isolate h

jim_thompson5910 · Answer

and in the next line I just flipped the equation

jim_thompson5910 · Answer

the last line is where I wanted you to fill it in (by evaluating with a calculator)

anonymous · Answer

oh I see now

jim_thompson5910 · Answer

yeah sorry I should have been more clear lol

jim_thompson5910 · Answer

what does 661.9/(pi*49) evaluate to?

anonymous · Answer

I don't think I did it right ugh

jim_thompson5910 · Answer

that's ok, post what you got

jim_thompson5910 · Answer

don't be afraid to get it wrong

that's what practice is for

anonymous · Answer

wait wait wait...is the / for dividing?

jim_thompson5910 · Answer

correct, 

ex: 10/5 = 10 divided by 5 = 2

anonymous · Answer

okay, hold on

jim_thompson5910 · Answer

alright

anonymous · Answer

10329.01274?

jim_thompson5910 · Answer

the 49 should be in the denominator

anonymous · Answer

im sooo confused

jim_thompson5910 · Answer

what kind of calculator are you using?

anonymous · Answer

scientific

jim_thompson5910 · Answer

and you're typing in 661.9/(pi*49) exactly as you see it?

jim_thompson5910 · Answer

an alternative is to use google as a calculator (if your calculator isn't cooperating) so you would type "661.9/(pi*49)" without quotes into google to get https://www.google.com/search?hl=&q=661.9%2F%28pi*49%29&sourceid=navclient-ff&rlz=1B3GGLL_enUS420US420&ie=UTF-8

jim_thompson5910 · Answer

what number does google give you as a result?

anonymous · Answer

4.2997...Aand so on

jim_thompson5910 · Answer

good, so that's the height

round that to the nearest tenth to get 4.3 inches

anonymous · Answer

woo! thank you!!

jim_thompson5910 · Answer

you're welcome