1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Alex_Xolod [135]
2 years ago
10

Jeff and Kirk can build a​ 75-ft retaining wall together in 4 hours. Because Jeff has more​ experience, he could build the wall

by himself 1 hour quicker than Kirk. How long would it take Kirk​ (to the nearest​ minute) to build the wall by​ himself?
Mathematics
2 answers:
oee [108]2 years ago
8 0

It will take Kirk about 8 hours 32 minutes to build the wall by himself.

<h3>What is Quadratic Polynomial?</h3>

Quadratic equations are second-degree algebraic expressions and are of the form ax² + bx + c = 0.

Here, Let k represent Kirk's time (in hours) to build the wall by himself. Then (k-1) is the time it takes for Jeff to build it. Their working-together rate in "walls per hour" is ...

 1/k +1/(k -1) = 1/4

Multiplying by 4k(k-1), we have ...

 4(k-1) +4k = k(k -1)

 k² -9k = -4 . . . . . . . . subtract 8k and simplify

 k² -9k +20.25 = 16.25 . . . . . add (9/2)² to complete the square

 k -4.5 = √16.25 . . . . . . . . . take the square root

 k = 4.5 +√16.25 ≈ 8.531129 . . . hours

The fractional hour is ...

 0.531129 × 60 min ≈ 31.9 min ≈ 32 min

Thus, It will take Kirk about 8 hours 32 minutes to build the wall by himself.

Learn more about Quadratic Polynomial from:

brainly.com/question/2350120

#SPJ1

LiRa [457]2 years ago
7 0

Answer:

  8 hours 32 minutes

Step-by-step explanation:

Working together, the construction rates add. We can use the given relation to write an equation for the total time when the pair work together.

__

<h3>setup</h3>

Let k represent Kirk's time (in hours) to build the wall by himself. Then (k-1) is the time it takes for Jeff to build it. Their working-together rate in "walls per hour" is ...

  1/k +1/(k -1) = 1/4

__

<h3>solution</h3>

Multiplying by 4k(k-1), we have ...

  4(k-1) +4k = k(k -1)

  k² -9k = -4 . . . . . . . . subtract 8k and simplify

  k² -9k +20.25 = 16.25 . . . . . add (9/2)² to complete the square

  k -4.5 = √16.25 . . . . . . . . . take the square root

  k = 4.5 +√16.25 ≈ 8.531129 . . . hours

The fractional hour is ...

  0.531129 × 60 min ≈ 31.9 min ≈ 32 min

It would take Kirk about 8 hours 32 minutes to build the wall by himself.

_____

<em>Additional comment</em>

For most "working together" problems the rates of completing work need to be expressed in jobs per unit time. Usually, the rates are given in terms of time per job, as they are here. That is why reciprocals get involved.

You might be interested in
A rectangle has an area of 45x2 − 42x − 48 and a width of 5x − 8. what is the length of the rectangle? to find the length of the
kondaur [170]

If the area and width of the rectangle are 45x² − 42x − 48 and (5x − 8) then the length of the rectangle will be (3x + 2).

<h3>What is a rectangle?</h3>

It is a polygon that has four sides. The sum of the internal angle is 360 degrees. In a rectangle, opposite sides are parallel and equal and each angle is 90 degrees. And its diagonals are also equal and intersect at the mid-point.

A rectangle has an area of 45x² − 42x − 48 and a width of 5x − 8.

Then the length of the rectangle will be

area = length × width

Then we have

Area = 45x² − 42x − 48

Then the factor of the polynomial will be

Area = (5x − 8)(3x + 2)

Then the length of the rectangle will be (3x + 2).

More about the rectangle link is given below.

brainly.com/question/10046743

4 0
2 years ago
Read 2 more answers
Find the value of x AND the value of each angle.
guapka [62]

Answer:

x=63

x+15=78

Step-by-step explanation:

180-102=78

78-15=63

x=63

x+15=78

5 0
2 years ago
In algebra, we use a(n) to represesent a veriable
nekit [7.7K]

Answer:

Are you Algebra 1 or 2?

Step-by-step explanation:

4 0
2 years ago
Read 2 more answers
I'll give the right answer brainliest hh. I would put all my questions in one question but for some reason brainly wont let me p
11Alexandr11 [23.1K]

Answer:

Picture is not clear please post a clear picture. Note brainly is meant to be <u>one</u><u> </u><u>question</u><u> </u>per post for further reference

6 0
2 years ago
Help me I need the math problem
miss Akunina [59]

Answer:

y=4x-3

Step-by-step explanation:

5 0
2 years ago
Read 2 more answers
Other questions:
  • 478 divided 16 using partial quotients
    13·2 answers
  • Negative 4 times -3/2
    11·2 answers
  • Examples: Determine if the graph is a function. If it is, state the domain and range.
    6·1 answer
  • BRIA is a rectangle. AN=5. NR=x-3. please solve for x, NR, and BI
    9·1 answer
  • 73,205÷29 how do I work this problem
    11·2 answers
  • How do you do this question?
    10·1 answer
  • If x= 3 what is the value of 50 - 2x?
    13·2 answers
  • The circumference of a circle is 16Pi ft.<br><br> The radius is ____ ft.
    7·2 answers
  • Multiply. Express in simplest form. 3/8 x 1/2
    10·1 answer
  • David bought 5/6 of a pound of candy. He would like to split it between his 5 friends. What fraction of the candy will each frie
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!