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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

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.

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


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

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?

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

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?

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

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
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
characteristics of micro business
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 ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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.
is Bucky paper clear?
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
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
anybody can imagine what will be happen after 100 years from now in nano tech world
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
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Selected topics in algebra. OpenStax CNX. Sep 02, 2015 Download for free at http://legacy.cnx.org/content/col11877/1.2
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