A circular pool measures 10 feet across. One cubic yard of concrete is to be used to create a circular border of uniform width around the pool. If the border is to have a depth of 4 inches, how wide will the border be?

Question

kainui · Answer

I suggest drawing out a picture, that will make it a little easier to think about.

anonymous · Answer

I have done that, but I can't figure out which formula I need to use, or really which direction to go. We focused on quadratics today in class, but nothing seems to make sense.

kainui · Answer

|dw:1401319059405:dw| So from here can you tell me what the total surface area of the border will be if w is the width of the border and r is the radius of the pool? It should be a nice little equation.

radar · Answer

|dw:1401319076954:dw|

radar · Answer

After you get the area of the border, multiply that by 1/3 foot (4 in.) and you will have volume of border in cu. ft.  Now make that equal to 27 (a cu. yd is 27 cu. ft)

radar · Answer

Solve for x or w as indicated in Kainui diagram, which is an excellent diagram.

radar · Answer

Make all units the same (I made feet common you may choose differently.

anonymous · Answer

Thank you all very much for your help. I believe I was able to figure it out. :)