Math Is Fun Forum

Sam_thing

Member

Registered: 2018-08-06

Posts: 4

Area of a pool

Hey, i would like some help on thus problem please.

5. Problem solver (worth 6 points):  Find the surface area and volume of the pool shown below when the sides, the twelve "bumpers" making up the perimeter of the pool, are 5 ft each and the depth of the pool is 6 ft.

here is a link to the picture of the pool: https://ibb.co/nwSdqe

I have already done some of the work but the teacher says that it was wrong.
Make a octagon and rectangular prism

a(tan(22.5))=(2.5/a)a

a(tan(22.5))=2.5/(tan(22.5))=(tan(22.5))

a=6.04

A=1/2(6.04)(40)(2)=481.6ft2

6.042+2.52=6.52

A=2((6.5x10)+(6x10)+(6x6.5))=328ft2

328+481.6=809.6ft2

total area is 809.6ft2

V=2(1+√2)52x6=724.3ft3

v=10x6x6.5=390ft3

724.3+390=1114.3ft3

Thank you for the help!!!

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Area of a pool

This has been asked before.  See http://www.mathisfunforum.com/viewtopic.php?id=23304

What on-line course is this from?

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Sam_thing

Member

Registered: 2018-08-06

Posts: 4

Re: Area of a pool

The only problem with that question is that it gives me hexagon instead of an octagon. In this problem i need to make an octagon and rectangular prism. Also it seems i cant see the work of any of the other people which makes it hard to grasp.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Area of a pool

hi Sam_thing

I'm struggling a bit with your working.  The octagon consists of 8 isosceles triangles.  If 'a' is the height of one of these then I agree with your answer.  So next I worked out the area of 8 of these triangles 8 times 2.5 times a.  Where did 40 come from ?

Please re-post your working with some notes at each line to say what you are calculating.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob