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Mathematics 13 Online
OpenStudy (anonymous):

Find the volume of the cone. (Round to the nearest tenth.) Answer 1250.7 mm 2014.1 mm3 289.4 mm3 1229.4 mm3

OpenStudy (anonymous):

OpenStudy (anonymous):

The formula you should use is \[V_{cone}=\frac{1}{3}\pi r^2 h\]

OpenStudy (anonymous):

radius is not clear

OpenStudy (anonymous):

i think it's 38

OpenStudy (anonymous):

There's a curvy arrow beside the 38, maybe it's circumference of the base?

OpenStudy (anonymous):

is 38 the radius ?

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

So \(C=2 \pi r\) first, and then the formula above, assuming 38 is the circumference. That would make the drawing more to scale as well.

OpenStudy (anonymous):

so whats the answer

OpenStudy (anonymous):

What part did you get stuck on?

OpenStudy (anonymous):

finding the answer

OpenStudy (anonymous):

Your first task is to find the radius. If you're given a circumference of 38, then you can find the radius with \(C=2 \pi r\).

OpenStudy (anonymous):

238.64

OpenStudy (anonymous):

but thats not an answer

OpenStudy (anonymous):

Hrm, my radius was much smaller than that. Could you post your calculation?

OpenStudy (anonymous):

2x3.14x38

OpenStudy (anonymous):

2*3.14*r = 38

OpenStudy (anonymous):

r = 38/6.28

OpenStudy (anonymous):

Where did that 14 come from? Perhaps we should rearrange the equation first \[C=2 \pi r <=> r=\frac{C}{2\pi}\]

OpenStudy (anonymous):

?

OpenStudy (anonymous):

If \[r=\frac{C}{2\pi}\] you just need to put 38 in for C, and find the value of the fraction.

OpenStudy (anonymous):

59.66?

OpenStudy (anonymous):

So you took 38, and divided it by 2\(\pi\), and got 59.66?

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

but its wrong

OpenStudy (anonymous):

im getting really confused

OpenStudy (anonymous):

The value of 2\(\pi\) is about 6.28, so if you divide 38 by 6.28, the number you get out should be smaller than 38.

OpenStudy (anonymous):

19

OpenStudy (anonymous):

nope

OpenStudy (anonymous):

That's 38 divided by 2. Divide that by \(\pi\)

OpenStudy (anonymous):

6.05

OpenStudy (anonymous):

yup

OpenStudy (anonymous):

Alright, now we're getting somewhere! Now you need to use the equation for the volume of a cone: \[V=\frac{1}{3}\pi r^2 h\]

OpenStudy (anonymous):

344.79

OpenStudy (anonymous):

yea

OpenStudy (anonymous):

so how do we get the answer

OpenStudy (anonymous):

1/3*3.14*(6.05)^2*9

OpenStudy (anonymous):

but thats nott the answer

OpenStudy (anonymous):

344.79 should be the answer, but for some reason it's not on the list you gave. I'm quite stumped.

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