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Practice set e

A study of the air quality in a particular city by an environmental group suggests that t years from now the level of carbon monoxide, in parts per million, in the air will be

A = 0.2 t 2 + 0.1 t + 5.1

(a) What is the level, in parts per million, now?

(b) How many years from now will the level of carbon monoxide be at 8 parts per million? Round to the nearest tenth.

(a). 5.1 parts per million (b). 3.6 years

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Sample set f

A contractor is to pour a concrete walkway around a swimming pool that is 20 feet wide and 40 feet long. The area of the walkway is to be 544 square feet. If the walkway is to be of uniform width, how wide should the contractor make it?

Step 1:  Let x = the width of the walkway.
Step 2:  A diagram will help us to get the equation.
    A rectangle with side length forty plus two x and width of twenty plus two x with an inner rectangle x units from the outside rectangle throughout. The length of the inner rectangle is labeled as forty and the width is labeled as twenty.
     (Area of pool and walkway) — (area of pool) = (area of walkway)
      ( 20 + 2 x ) ( 40 + 2 x ) 20 · 40 = 544
Step 3: ( 20 + 2 x ) ( 40 + 2 x ) 20 · 40 = 544 800 + 120 x + 4 x 2 800 = 544 120 x + 4 x 2 = 544 4 x 2 + 120 x 544 = 0 Divide each term by 4 . x 2 + 30 x 136 = 0 Solve by factoring . ( x 4 ) ( x + 34 ) = 0 (This is difficult to factor so we may  wish to use the quadratic formula .) 
      x 4 = 0 or x + 34 = 0 x = 4 or x = 34  has no physical meaning .
Check a width of 4 feet as a solution.
      Step 4: Area of pool and walkway  = ( 20 + 2 · 4 ) ( 40 + 2 · 4 ) = ( 28 ) ( 48 ) = 1344
     Area of pool = (20)(40) = 800
     Area of walkway = 1344 800 = 544 Yes, this is correct .
     This solution checks.
Step 5:  The contractor should make the walkway 4 feet wide.

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Practice set f

A contractor is to pour a concrete walkway around a swimming pooi that is 15 feet wide and 25 feet long. The area of the walkway is to be 276 square feet. If the walkway is to be of uniform width, how wide should the contractor make it?

3 ft wide

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Exercises

Some of the following problems have actual applications and some are intended only as logic developers. A calculator may be helpful. The problems appear in groups and correspond to the noted Sample Set problem.

Sample set a—type problems

The manufacturer of electronic fuel injectors determines that the number N of injectors sold is related to the price x per injector by N = 22 x x 2 . At what price should the manufacturer price the injectors so that 112 of them are sold?

$ 8 or $ 14

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The owner of a stained-glass shop determines that the number N of pieces of a particular type of glass sold in a month is related to the price x per piece by N = 21 x x 2 . At what price should the shop buyer price the glass so that 162 sell?

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It is estimated that t years from now the population of a certain city will be

P = t 2 15 t + 12 , 036

(a) What is the population now?

(b) How many years from now will the population be 12,000?

(a)  12 , 036   (b)  3  and  12  years from now

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It is estimated that t years from now the population of a certain city will be

P = t 2 16 t + 24 , 060

(a) What is the population now?

(b) How many years from now will the population be 24,000?

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If an object is thrown vertically upward, its height h , above the ground, in feet, after t seconds is given by h = h 0 + v 0 t 16 t 2 , where h 0 is the initial height from which the object is thrown and v 0 is the initial velocity of the object. Using this formula and an approach like that of Sample Set A, solve this problem.

A ball thrown vertically into the air has the equation of motion h = 48 + 32 t 16 t 2 .

(a) How high is the ball at t = 0 (the initial height of the ball)?


(b) How high is the ball at t = 1 (after 1 second in the air)?


(c) When does the ball hit the ground? ( Hint: Determine the appropriate value for h then solve for t .)

(a)  48  feet  (b) 64 feet  (c)  t = 3

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Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
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how to fabricate graphene ink ?
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for screen printed electrodes ?
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of graphene you mean?
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or in general
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in general
s.
Graphene has a hexagonal structure
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what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
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Cied
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I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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what is the function of carbon nanotubes?
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Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
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AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
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In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
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anybody can imagine what will be happen after 100 years from now in nano tech world
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after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
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silver nanoparticles could handle the job?
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not now but maybe in future only AgNP maybe any other nanomaterials
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this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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Source:  OpenStax, Elementary algebra. OpenStax CNX. May 08, 2009 Download for free at http://cnx.org/content/col10614/1.3
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