SOLUTION: You just had a pool installed that has dimensions 10 feet by 24 feet by 4 feet. You want to install a cement patio all the way around the pool that extends the same distance around

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Question 1073062: You just had a pool installed that has dimensions 10 feet by 24 feet by 4 feet. You want to install a cement patio all the way around the pool that extends the same distance around every side of the pool. A cement truck holds enough cement to cover 810 square feet at a 4-inch depth. If you don't want to have to pay for a second truck, what is the widest you can make the patio around your new pool?
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
-solution removed-
Mistook outer patio for inner patio

Answer by ikleyn(52788) About Me  (Show Source):
You can put this solution on YOUR website!
.
You just had a pool installed that has dimensions 10 feet by 24 feet by 4 feet. You want to install a cement patio all the way
around the pool that extends the same distance around every side of the pool. A cement truck holds enough cement to cover
810 square feet at a 4-inch depth. If you don't want to have to pay for a second truck,
what is the widest you can make the patio around your new pool?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The outer dimensions of the patio are (10+2x) feet wide and (24+2x) feet long.
The area of this rectangle is (10+2x)*(24+2x) square feet.
The area of the pool surface (which obviously is not covered by cement) is 24*10 square feet.

The difference of the areas is the area of the cement patio all the way around the pool. So, this area is

(10+2x)*(24+2x) - 10*24 = 4x%5E2+%2B68x+%2B+10%2A24+-+10%2A24 = 4x%5E2+%2B+68x.

So your equation is

4x%5E2+%2B+68x = 810,

4x%5E2+%2B+68x+-+810 = 0,

x%5B1%2C2%5D = %28-68+%2B-+sqrt%2868%5E2+-+4%2A4%2A%28-810%29%29%29%2F%282%2A4%29 = %28-68+%2B-+132.6%29%2F8.

The only positive root is x = %28-68%2B132.6%29%2F8 = 8.1 ft.

Answer.  The width of the patio is approximately 8.1 ft all the way around the pool.

Check.   (10+2*8.1)*(24+2*8.1) - 10*24 = 813.24 ft^2 which is close enough.


The solution by "josgaritmetic" is  a)  highlight%28WRONG%29  and  b)  highlight%28ABSURD%29  starting from his very first equation.


For many other similar solved problems see the lessons
    - Problems on the area and the dimensions of a rectangle surrounded by a strip
    - Problems on a circular pool and a walkway around it
in this site.

Also,  you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic
"Dimensions and the area of rectangles and circles and their elements".