volume of a cylinder

[Ruiz007]

Hi I need help!! :x
I need step by step help with this problem... How may cubic yards of dirt must be dug to make a well 4 feet 6 inches in diameter and 42 feet deep? Thank you!

 

[galactus]

About 25 yards.

 

[Deleted member 4993]

Hi I need help!! :x
I need step by step help with this problem... How may cubic yards of dirt must be dug to make a well 4 feet 6 inches in diameter and 42 feet deep? Thank you!

You should convert all the given dimensions to inches - then find the volume of the well.

What is the volume of the well in cubic inches? ..............................................(1)

How many cubic inches are there in a cubic yard?............................................(2)

Divide (1) by (2) to get your answer.

 

[galactus]

Not to appear contradictory, but I do not believe it is necessary to convert to inches (though, one certainly can if they wish). There are 27 cubic feet in a cubic yard, so just find the volume, as is, in cubic feet, then divide by 27.

Since the diameter is 4.5 feet, then the radius is 2.25 feet.

$\displaystyle \frac{{\pi}(2.25)^{2}(42)}{27}$

 

[Deleted member 4993]

Not to appear contradictory, but I do not believe it is necessary to convert to inches (though, one certainly can if they wish). There are 27 cubic feet in a cubic yard, so just find the volume, as is, in cubic feet, then divide by 27.

Since the diameter is 4.5 feet, then the radius is 2.25 feet.

$\displaystyle \frac{{\pi}(2.25)^{2}(42)}{27}$

Not at all contradictory - I just feel comfortable working with inches - I somehow visualize it better. As you have said it is just two different (correct) approaches to the same problem.

 

[BigGlenntheHeavy]

$\displaystyle Without \ a \ calculator, \ which \ would \ you \ rather \ reduced:$

$\displaystyle \frac{42\pi(2.25)^2}{27}(ft.), \ \frac{504\pi(27)^2}{46656}(in.), \ or \ \frac{1280.16\pi(68.58)^2}{764554.857984}(cm.)?$

$\displaystyle The \ reason \ for \ my \ above \ statement \ is \ since \ Subhotosh \ Khan \ feels \ more \ comfortable \ working$

$\displaystyle with \ inches \ instead \ of \ feet; \ maybe \ he \ feels \ more \ comfortable \ still \ working \ with \ centimeters$

$\displaystyle instead \ of \ inches.$

 

[Denis]

$\displaystyle Without \ a \ calculator, \ which \ would \ you \ rather \ reduce ?:$

$\displaystyle \frac{42\pi(2.25)^2}{27} \ or \ \frac{504\pi(27)^2}{46656}?$

Please share your work with us, indicating exactly where you are stuck - so that we may know where to begin to help you.

 

[BigGlenntheHeavy]

$\displaystyle Denis, \ you're \ OK.$

 

[Denis]

So are you, BigG, so are you...