English Deutsch Français Italiano Español Português 繁體中文 Bahasa Indonesia Tiếng Việt ภาษาไทย
All categories

A pool in the shape of a circle measures 10 feet across. One cubic yard of concrete is to be used to create a circular boarder of uniform width around the pool. If the boarder is to have a depth of 3 inches, how wide will the boarder be? ( a cubic yard = 27 cubic feet) the answer is 2.71 ft wide...i jus need to know how to actually do the work..thanks

2007-09-05 16:42:53 · 6 answers · asked by Richard C 1 in Science & Mathematics Mathematics

i dont get it

2007-09-05 16:49:00 · update #1

6 answers

brp its simple all you do is add a decimal then for every cubic yard u add a invisible zero then you place the decimal behind the second number

2007-09-05 16:46:19 · answer #1 · answered by Anonymous · 0 0

Envision the area to be filled as the difference between the area of an outer circle of unknown diameter and the inner circle with a diameter of 10 ft. The volume of concrete, which we know is 1 yd^3, is the difference between these two areas multiplied by the depth of 3 inches.

So I'll convert all of my units to feet and set up a volume equation to find the radius of the outer circle, then subtract 5 ft (the radius of the inner circle) from that to get the width of the boundary. Here are some terms and values:
R1 = 5'
R2 = radius of the outer circle
D = depth of concrete = 3" = .25'
V = (1 yd)^3 = 27 ft^3

The basic equation is:
V= D[pi(R2^2) - pi(R1^2)]
27 = .25pi(R2^2 - 5^2)

Solving gives R2 = 7.706
The width of the border = R2 - R1 = 7.71ft - 5 ft = 2.71 ft

2007-09-05 17:09:52 · answer #2 · answered by spineocylinder 2 · 0 0

The volume of the boarder is like a hollow cylinder

Let w = width of boarder
the base is pi*(5+w)^2 - 5^2 = pi*(w^2 + 10w)

Hight = 3 in = 1/4 ft.
Volume = pi*(w^2 + 10w) X 1/4

Eq to solve = pi*(w^2 + 10w) x 1/4 = 27
w^2 + 10w -34.37 = 0

Using the quad formula, you should find w = 2.7

2007-09-05 17:10:35 · answer #3 · answered by norman 7 · 0 0

A calculus problem? If you draw a diagram of the train just as the front of the train lines up with the man and then 5 seconds later, where the end of the train lines up with the man, the length of the train+distance man travels in passing time= speed* passing time SO................ LT+ 4*(88/60)*5 = 30*(88/60)*5. The term 88/60 converts mph to fps. Then LT = 26*60*5/88

2016-05-17 19:17:11 · answer #4 · answered by ? 2 · 0 0

You would set it up as:

V=((pi)R^2-(pi)r^2)*h

where:

R=outer radius
r=inner radius
h=depth

You would plug in your values, and solve for R. After you've found that, you would subtract the inner radius to find your width.

2007-09-05 16:59:18 · answer #5 · answered by www 2 · 0 0

www.webmath.com might help...

2007-09-05 16:50:25 · answer #6 · answered by Anonymous · 0 0

fedest.com, questions and answers