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#1 2013-01-12 18:01:44

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

please help give detailed solutions

A dungeon is constructed with a rectangular floor 10m by 20m. The walls are vertical and 30m high. If there are windows, find:
a. total area of the ceiling walls and floor
b. the storage space of the dungeon

The manufacturer of tin cans received an order of 100,000 cylindrical tin cans of height 12cm and diameter 8cm how many square meters of tin cans?
A pyramid has its vertex at the center of a cube and its base coincidence with a surface with a face of the cube. Find the angle that each lateral face of the pyramid makes with base of the pyramid?

A hemisphere soup bowl 20 cm in diameter is filled with soup  to depth of 6 cm.
a. find the volume of the soup.
b. what percentage of the capacity of the bowl is filled.

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#2 2013-01-12 19:29:19

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi alvlad1022

Welcome to the forum.

The internet has lots of sites that will do your homework for you and charge you.

The MIF forum doesn't charge,  but we don't just do someone's homework either!  Sorry. 

But I'll lead you through these one by one, if you are willing to do some work too.

Q1

A dungeon is constructed with a rectangular floor 10m by 20m. The walls are vertical and 30m high. If there are ^no windows, find:
a. total area of the ceiling walls and floor
b. the storage space of the dungeon

So there are six areas altogether.  eg. floor area = 10 x 20 = ceiling area.

Long walls are 20 x 30 and  I'll leave you to figure out the short walls.

So calculate the six areas and add them up.

The storage space is the same as the volume so calculate length x width x height.

When you've got two answers, post them back for checking and I'll go on to Q2.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#3 2013-01-12 19:45:14

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

the ceiling area = 2lw = 2lw
                       = 2 (10*30) + 2(20*30)
                       = 600 + 1200
                       = 1800 m

V= LWH
   = 20*10*30
   = 6000 m total storage space of the dungeon

is this correct. thaks

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#4 2013-01-12 20:02:15

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi alvlad1022

The volume (storage) is correct.  But write

600 and 1200 are also correct for the four walls.  But add the floor area and ceiling area too.

Q2.

The manufacturer of tin cans received an order of 100,000 cylindrical tin cans of height 12cm and diameter 8cm how many square meters of tin cans?

The radius of the top is 4cm.

So to get the surface area of one can, first the top and bottom:

plus the curved surface area (imagine the can is unrolled to make a rectangle 12 by circumference )

Add these answers to get the total surface area.

Then x by 100 000 for all the cans.

Now you have the answer in square cm.

A square metre is 100cm by 100cm = 10 000 square cm.

So to convert your answer to square metres, divide by 10 000.

Q3.  Have a look at the picture below (click to enlarge).  Is that the correct model for this question ?

Bob

View Image: pyramid in cube.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#5 2013-01-12 22:17:17

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

Q3 image model was right but i still confused with the answer of Q2 my prof, give me the answer for the problem it was = 4101.24 m^2

i try many ways to solve it but still i fall the same answer as you did.

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#6 2013-01-12 22:25:25

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi

Have a look at

http://www.mathsisfun.com/geometry/cylinder.html

So if you add together the top, bottom and curved surface you get:

I'm getting 4021 m^2 for the tins

Q3.

To see the true angle between face VAB and the base ABCD you have to look along the line of intersection, AB

The first picture below shows the points, and the second shows the view along AB.  You cannot see A because it is exactly behind B

If the size of an edge of the cube is 2S then the distance along the base to the point directly under V is S.

The angle you want can be found by tangents.

Bob

ps.  I'm out now to a show rehearsal so I won't be able to reply until about 5pm GMT.

View Image: pyramid in cube.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#7 2013-01-12 23:05:11

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

thank  you so much

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#8 2013-01-13 05:05:11

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi alvlad1022

I'm back.  Do you have some answers?

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#9 2013-01-15 23:55:29

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

Need some help about the current issues, problems, and development in solid geometry and trigonometry.
please... any links or site where can i search this.


Thank you..

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#10 2013-01-16 00:08:05

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi alvlad1022

That depends on exactly what you want.  You could start by looking at the MathsIsFun teaching pages:

http://www.mathsisfun.com/

I also find Wikipedia can be quite helpful.

http://en.wikipedia.org/wiki/Main_Page

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#11 2013-01-17 11:10:01

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

Thanks a lot..

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#12 2013-01-22 23:08:07

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

do you have any idea how to find the number of degrees in the angle at which the diagonal of the cube intersect.

thank you.

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#13 2013-01-23 01:31:33

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi alvlad1022

Diagram below.

I think this angle will be AIB on my diagram.

If you call the length of a side x, then you can use Pythag to get AG and then half it to get AI (and BI)

Triangle AIB is isosceles so the midpoint of AB (M) will enable you to make a right angled triangle, AMI.

Should be able to use trig to get half the angle you want.

Bob

View Image: cube.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#14 2013-03-19 02:14:54

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

Find the area of the largest equilateral triangle that can be inscribed
in a circle whose diameter is 20 cm. can you show me how to solve it please

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#15 2013-03-19 02:17:14

alvlad1022
Member
Registered: 2013-01-12
Posts: 9

Re: please help give detailed solutions

i am having a demo teaching in our school can you help me how to make detailed lesson plan for the 4th quarter my topic is factoring



thanks...

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#16 2013-03-19 04:56:12

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,269

Re: please help give detailed solutions

hi

Use Pythagoras (see diagram)

Bob

View Image: alvlad.gif

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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