Measuring Problems...Need help asap!! Thank you in advance

[newyorkstylez08]

I have a couple questions. Even if you can only answer 1 or 2 I would greatly appreciate it.

1. A typical unit of measure for hydrologists is the acre-foot of water. Determine the number of m3 in one acre foot if there are 640 acres in a square mile, 5280 feet in a mile and 2.54cm to an inch.

2. A beautiful white pearl has a diameter of 6mm. Determine the surface area of the pearl and the volume of the pearl given the following formulas:

Volume(sphere)= 4/(3 ) ?r^3

Surface Area(sphere)= 4?r^2

3. Eight turns of wire are wrapped around a pipe with a length of 20cm and a circumference of 6cm. What is the length of the wire?

 

[tutor_joel]

These are unit conversion problems or dimensional analysis.

1. if there are 640 acres in a square mile, that means 640 square acre lots fit into a square 1 mile by 1 mile. So, how many square feet in a mile? Think length times width. Draw it out to visualize it if you have to. Then how many square feet in an acre?

2. Simple, just plug and chug after finding the radius

3. If a wire can turn around around a pipe 8 times and each turn has a circumference of 6 cm...?

 

[newyorkstylez08]

Thank you so much!
Math is not my best subject.
I figured out number 1.

I'm still having trouble with number 3 for some reason

 

[LivingMath]

#3. The circumference around a pipe (or any cylinder) is just the length around it. You can think of it like walking around a circle of circumference 6m. If you walk around the circle 8 times, how far have you walked?