Answer:
Step-by-step explanation:
5 * 5 * 5 * 5 * 5 = 5^5
Written in Latex, which is the best way to show this, the answer is
[tex]5^{5}[/tex]
I think you might mean B. If you do then it is correct, but it must be shown as 5^5
what is one root of this equation 2x^2-4x+9=0?
A. -2+sqrt14/2i
B. -1+sqtr14/2i
C. 1+sqrt14/3i
D. 1+sqrt14/2i
E. 2+sqrt14/2i
For this case we have the following quadratic equation:
[tex]2x ^ 2-4x + 9 = 0[/tex]
The solutions are given by:
[tex]x = \frac {-b \pm \sqrt {b ^ 2-4 (a) (c)}} {2a}[/tex]
We have to:
[tex]a = 2\\b = -4\\c = 9[/tex]
Substituting:
[tex]x = \frac {- (- 4) \pm \sqrt {(- 4) ^ 2-4 (2) (9)}} {2 (2)}\\x = \frac {4 \pm \sqrt {16-72}} {4}\\x = \frac {4 \pm \sqrt {-56}} {4}\\x = \frac {4 \pm \sqrt {-1 * 56}} {4}\\x = \frac {4 \pmi \sqrt {2 ^ 2 * 14}} {4}\\x = \frac {4 \pm2i \sqrt {14}} {4}\\x = \frac {2 \pm i\sqrt {14}} {2}[/tex]
Answer:
[tex]x_ {1} = \frac {2 + i \sqrt {14}} {2}\\x_ {2} = \frac {2-i \sqrt {14}} {2}[/tex]
Answer:
OPTION E: [tex]\frac{2+\sqrt{14}i}{2}[/tex]
Step-by-step explanation:
Given the Quadratic equation [tex]2x^2-4x+9=0[/tex], you can find the roots by applying the Quadratic formula. This is:
[tex]x=\frac{-b\±\sqrt{b^2-4ac} }{2a}[/tex]
In this case you can identify that:
[tex]a=2\\b=-4\\c=9[/tex]
Then you can substitute values into the Quadratic formula:
[tex]x=\frac{-(-4)\±\sqrt{(-4)^2-4(2)(9)} }{2(2)}[/tex]
[tex]x=\frac{4\±\sqrt{(56} }{4}[/tex]
Remember that [tex]\sqrt{-1}=i[/tex], then:
[tex]x=\frac{4\±2\sqrt{14}i}{4}[/tex]
Simplifying, you get:
[tex]x=\frac{2(2\±i\sqrt{14}i)}{4}\\\\x=\frac{2\±\sqrt{14}i}{2}\\\\\\x_1=\frac{2+\sqrt{14}i}{2}\\\\x_2=\frac{2-\sqrt{14}i}{2}[/tex]
The length of a rectangle is three times its width. If the perimeter is at most 112 centimeters, what is its greatest possible value for width?
Answer:
width = 14 , length = 42
Step-by-step explanation:
Here we have to find the width of the rectangle using the fact that length is 3 times the width and perimeter is given
Let the length of the rectangle = x
Hence the width of the rectangle = 3 x
The formula for the perimeter is
P=2(l+b)
Given P = 112
Hence
112=2(l+b)
l+b=56
substituting values of l and b in this
x+3x= 56
4x=56
x=14
Hence width = 14 cms
length = 3*14 = 42 cms
For which value of O is sin O= -1
Answer:
O = 2 π n - π/2 for n element Z
Step-by-step explanation:
Solve for O:
sin(O) = -1
Hint: | Eliminate the sine from the left hand side.
Take the inverse sine of both sides:
Answer: O = 2 π n - π/2 for n element Z
assuming you meant sin(θ) = -1, Check the picture below.
1
2.1.3 Quiz: What is a Function?
Question 7 of 10
2 Ports
The amount of time it takes to complete a reading assignment might be a
function of which of the following?
O
A. The cost of the book
O
B. The year the book was published
O
C. The number of pages in the assignment
Answer:
C. The number of pages in the assignment.
A function is an expression that defines the relationship between two variables. The amount of time it takes to complete a reading assignment might be a function of the number of pages in the assignment. So, option C is correct.
What is a function?A function is an expression, that states the relationship between the variables in that expression.
Ley m and n are two variables and are related to each other with a function, f(m) = n.
So, the variable m is called the independent variable and the variable n is called the dependent variable.
Given statement:The given statement is "The amount of time it takes to complete a reading assignment might be a function of-"
From the options,
cost of the variable does not affect the time required to read and the year of publishing also does not affect the time required to read. But the number of pages in the assignment affects the time required to read. As the number of pages increases, the time required to read them also increases, and as the number of pages decreases, the time required to read them also decreases.So, here the time is a dependent variable, and the number of pages in the assignment will be the independent variable.
Thus, option c is correct.
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The list shows the final exam grades for Ms. Gold's math class. Make a stem-and-leaf plot for the data.
66,98,92,91,69,55,53,90,67,74,57,58,60,59,86,92,63,55,51,84
To create a stem-and-leaf plot, first, we need to organize the data into stems (tens digit) and leaves (ones digit). For the given data, we can organize it as follows:
How to solveStem | Leaf
5 | 1 3 5 5 7 8 9
6 | 0 3 6 7 9
7 | 4
8 | 4 6
9 | 0 1 2 2 8
The data is then demonstrated by a stem-and-leaf plot as follows:
51, 53, 55, 55, 57, 58, 59, 60, 63, 66, 67, 69, 74, 84, 86, 90, 91, 92, 92, 98
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A sequence is defined by the following:
A1 = 6 and an = -1.2n-1
What is the 4th term?
-12.4416
-10.368
10.368
12.4416
Answer:
Step-by-step explanation:
a1 = 6
a2 = -1.2*a_(n-1)
a2 = -1.2*a_1
a2 = -1.2 * 6
a2 = -7.2
a3 = -1.2*a_(n-1)
a3 = -1.2*a_2
a3 = -1.2 * - 7.2
a3 = 8.64
a4 = -1.2 * a_3
a4 = -1.2 * 8.64
a4 = -10.368
Answer: The correct option is (B) -10.368.
Step-by-step explanation: Given that a sequence is defined b the following :
[tex]a_1=6,~~~a_n=-1.2a_{n-1}.[/tex]
We are to find the 4-th term.
To find the fourth term, we need to start from finding the first term.
If n = 2, then the second term is given by
[tex]a_2=-1.2\times a_1=-1.2\times 6=-7.2.[/tex]
If n = 3, then the third term is given by
[tex]a_3=-1.2\times a_2=-1.2\times (-7.2)=8.64.[/tex]
If n = 4, then the fourth term is given by
[tex]a_4=-1.2\times a_3=-1.2\times 8.64=-10.368.[/tex]
Thus, the fourth term of the given sequence is -10.368.
Option (B) is CORRECT.
I need help with this one too
Answer:
B
Step-by-step explanation:
I'm pretty sure that the shaded space represents all possible solutions, meaning that the X has to be greater than or equal to 2.
Four ounces of oregano and 2 ounces of garlic powder are mixed to create a poultry seasoning. Oregano costs $4 per ounce, and garlic powder costs $3 per ounce. The table shows the costs of the ingredients.
What is the value of y in the table?
THE ANSWER IS 6
Answer:
y = $6
Step-by-step explanation:
In the image below, the table of your question is attached
Based on the information presented in the table.
1 ounce of oregano costs $4
Because there are 4 ounces, this means that
x = 4*($4) = $16
1 ounce of garlic powder $3
Because there are 2 ounces, this means that
y = 2*($3) = $6
Total cost of the ingredients = x+y = 22 $
Bag A contains 3 white marbles and 2 red marbles. Bag B contains 6 white marbles and 3 red marbles. A person draws
one marble from each bag. Find the probability that both marbles are white.
2/5
3/5
9/14
Answer:
[tex]\frac{2}{5}[/tex]
Step-by-step explanation:
Bag A:
White = 3
Total = 3 White + 2 Red = 5
Prob (white marble from A) = [tex]\frac{3}{5}[/tex]
Bag B:
White = 6
Total = 6 White + 3 Red = 9
Prob (white marble from B) = [tex]\frac{6}{9}[/tex]
Prob (white from Bag A and white from Bag B)
= Prob (white marble from A) x Prob (white marble from B)
= [tex]\frac{3}{5}[/tex] x [tex]\frac{6}{9}[/tex]
= [tex]\frac{2}{5}[/tex]
What is the range of the given function?
O {x|x = -5, 1, 4, 6}
O {yl y=-7,-1, 0, 9}
O {x|x = -7, -5, -1,0, 1, 4, 6, 9}
O yly=-7, -5, -1, 0, 1, 4, 6, 9}
|__x__|__y__|
|_-5__|__9__|
|_1___|__0__|
|_4___|__-7_|
|_6___|__-1_|
(table above^)
Answer:
Step-by-step explanation:
we know that
The Domain of the function are all the values of x that can take the function
in this problem the domain is
The Range of the function are all the values of y that can take the function
in this problem the range is
therefore
{y | y = –7, –1, 0, 9} baaaam
know my brain hurts i hope this helped because i really tried haha sorry if it doesnt
Virginia drew the figure at the right on the board. The steps below are used to solve for the unknown angle, x, in the figure but are not arranged in the correct order.
1·) x= 15
2.) 75 + 15= 90
3,) 75+x= 90
4,) 75-75 + x = 90-75
Which sequence shows the correct order of the steps Virginia should follow to find the measure of the unknown
A 1234
B 3412
C 4213
D 2314
Answer:
Option B 3412
Step-by-step explanation:
we know that
step 1
75°+x=90° -----> by complementary angles
step 2
Solve for x
Subtract 75 both sides
75°-75°+x=90°-75°
step 3
x=15°
step 4
Verify
Substitute the value of x in the equation of the step 1
75°+15°=90°
90°=90° ----> is correct
therefore
The correct order is
3-4-1-2
f(x)x^2-2x and g(x)=6x+4 for which value of x does (f+g)(x)=0
Answer:
(f+g)(x)
Step-by-step explanation:
(f+g)(x)=
[tex] {x}^{2} - 2x + 6x + 4 = {x}^{2} + 4x + 4[/tex]
[tex](x + 2)(x + 2) = 0[/tex]
[tex](x + 2) = 0 \\ x = - 2[/tex]
Say your car doesn’t run on straight gasoline and you have to mix the oil with gas together in a specific ratio of 2.4 fl oz of oil for every gallon of gasoline. If you have 1.5 gallons of gas, how much oil should you add?
Answer:
3.6 fl oz
Step-by-step explanation:
figure out the percentage of the gallon that was used in the original ratio, in this case 1 that was used in 1.5. thats 150%
so no multiply 2.4 by 1.5 to get 3.6
to check work divide both ratios and see if its the same number (i checked)
For 1.5 gallons of gasoline, you should add 3.6 fluid ounces of oil to maintain the required ratio of 2.4 fl oz of oil per gallon of gas.
To calculate how much oil is needed for 1.5 gallons of gasoline when the mixture requires 2.4 fl oz of oil per gallon of gasoline, one can use a simple proportion:
2.4 fl oz oil / 1 gallon of gas = x fl oz oil / 1.5 gallons of gas
Solve for x to find the amount of oil needed for 1.5 gallons of gas:
x = 2.4 fl oz oil * 1.5 gallons of gas
We can multiply 2.4 fl oz by 1.5 to get the amount of oil:
x = 3.6 fl oz oil
Therefore, you should add 3.6 fluid ounces of oil to your 1.5 gallons of gasoline to achieve the correct mixture.
Determine the linear equation from the graph below.
1 Height of a balloon
3
+
.
.
.
.
.
Height (1000 ft)
10 20 30 40 50 60
Time (sec)
Answer: [tex]y=\frac{1}{30}x+1[/tex]
Step-by-step explanation:
The equation of the line in Slope-Intercept form is:
[tex]y=mx+b[/tex]
Where "m" is the slope and "b" is the y-intercept.
The slope of the line can be calculated with this formula:
[tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]
Pick to points of the given line. You can choose the point (60,3) and the point (30,2).
Then, substituting into the formula, you get:
[tex]m=\frac{2-3}{30-60}=\frac{1}{30}[/tex]
You can observe in the graph that the line intercepts the y-axis at the point (0,1), therefore "b" is:
[tex]b=1[/tex]
Substituting the slope and the y-intercept found into [tex]y=mx+b[/tex], you get the equation of this line:
[tex]y=\frac{1}{30}x+1[/tex]
Where "y" represents the Height (1,000 ft) and "x" represents the Time in seconds.
Answer:
The equation of the given line is :y = 0.04x + 0.6.
Step-by-step explanation:
From the given data , we can select two coordinates to determine the equation of the given line:
Let the point be [tex](10,1),(60,3)[/tex]
The equation of the line will be determined by the help of point slope form:
Slope of the line = [tex]m=\frac{y_2-y_1}{x_2-x_1}[/tex]
[tex](y-y_1)=m(x-x_1)[/tex]
The equation of the line is :
[tex]m=\frac{3-1}{60-10}=\frac{2}{50}=0.04[/tex]
[tex](y-1)=0.04(x-10)[/tex]
[tex]y-1=0.04x-0.4[/tex]
[tex]y=0.04x+0.6[/tex]
The equation of the given line is :y = 0.04x + 0.6.
in the parallelogram, angle QRP = 32 and angle PRS = 84. find angle PQR.
Aretha wanted to gather data about the cost of local bowling leagues in her area. She plotted the data and determined that the average bowling league costs consist of a one-time registration fee and a monthly fee modeled by the equation y = 15x + 20.
Identify and interpret the y-intercept in this model.
The y-intercept is 20. This is the cost per month.
The y-intercept is 20. This is the cost of registration.
The y-intercept is 15. This is the cost of registration.
The y-intercept is 15. This is the cost per month.
Answer:
B
Step-by-step explanation:
Answer: Option B) The y-intercept is 20. This is the cost of registration.
Given model is: y = 15x + 20.
We compare this equation with y = mx + b.
So,
the slope = m = 15.
y-intercept = b = 20.
Given: The cost consist of a one-time registration fee. It means the fixed cost is the one-time registration fee. It will also be the y-intercept.
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An indoor sport exhibition is coming to the arena. Your supervisor has asked you to help set up a handball pitch and seating area as shown in the plan view below..
Use the following formulae:
Perimeter of a rectangle = 2l + 2w
Circumference of a circle = πd
π = 3.14
Area of a rectangle = lw
Area of a circle = πr²
What is the total perimeter of the pitch and seating area?
m
What is the total area of the pitch and seating area?
m2
Answer:
Perimeter: 174.8 m
Area: 1,394 sq m
Step-by-step explanation:
First, the perimeter.
Before we start, let's calculate the circumference of the half-circles at the ends of the field.
The measurement says 2,000 cm, so let's convert it to 20 m for ease.
Circumference of a circle: πd, where d = diameter.. in our case d = 20 m
Circumference of a 20m diameter circle: 20π = 62.8 m
We have 2 half circles... so the perimeter of each half-circle will be: 31.4 m
We also have 800 cm measurement for the "height" of the seating areas... let's convert that in 8 m
We also need to find out the space between the seating area... We know the whole rectangular pitch is 40 m, then we have to subtract the width of both seating areas (20 and 15 m)... so the space between them is 5m
So, starting with the upper left corner of the rectangular pitch, and working our way clockwise, we encounter the following lengths:
P = 40 + 31.4 + 8 + 10 + 8 + 5 + 8 + 25 + 8 + 31.4 = 174.8 m
The total perimeter is then of 174.8 m
For the area, we need to calculate the area of all forms:
Large rectangular pitch:
LR = 40 x 20 = 800 sq m
The two half circles, form a circle, so A = πr², where r is the radius, which is half the diameter.
AC = π (10)² = 100 π = 314 sq m
Then the seating areas:
SA1 = 25 x 8 = 200 sq m
SA2 = 10 x 8 - 80 sq m
Then, we add up everything:
TA = LR + AC + SA1 + SA2
TA = 800 + 314 + 200 + 80 = 1,394 sq m
milk and cream are mixed together for a recipe. the total volume of the mixture is 1 cup. if the milk contains 2% fat, the cream contains 18% fat, and the mixture contains 6% fat, how much cream is in the mixture?
Answer:
answer is 1/4 cup
Step-by-step explanation:
Answer:
Amount of cream in cups [tex]=\frac{1}{4}[/tex]
Step-by-step explanation:
Let x be the amount of cream in cups.
Amount of milk = 1 - x cups.
The milk contains 2% fat and cream contains 18% fat.
The mixture contains 6% fat, so we have
[tex]1 \times \frac{6}{100}=x \times \frac{18}{100}+(1-x) \times \frac{2}{100}\\\\6=18x+2-2x\\\\16x=4\\\\x=\frac{1}{4}[/tex]
Amount of cream in cups [tex]=\frac{1}{4}[/tex]
A deli owner sold 90 sandwiches in one day. Of those sandwiches, 36 were pastrami.
Write and solve an equation to show what percent of sandwiches sold were pastrami.
Drag tiles to complete the equation. Tiles may be used once or not at all.
303640455490
p •
= 36
p =
%
Answer: 40%
Step-by-step explanation:
You can set up a ratio to help you solve the problem. See the paper attached. (:
The percentage of pastrami sold was 40 %
What is Percentage?
A percentage is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, %
Given data ,
Number of sandwiches sold in one day = 90
Number of pastrami in 90 sandwiches = 36
To calculate the percentage of pastrami in sandwiches , we divide the total number pastrami to the total number of sandwiches and multiply by 100
So , percentage of pastrami = ( 36 / 90 ) x 100 %
= ( 4 / 10 ) x 100 %
= 4 x 10 %
= 40 %
Hence , The percentage of pastrami sold was 40 %
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Need answer ASAP please! X=
1
3
7
Answer: i believe its 3
Step-by-step explanation:
Answer:
The correct answer is second option
3
Step-by-step explanation:
From the figure we can see that, a circle.
The two lines from a point cut the circle.
To find the value of x
From the figure we can write, the products of parts of line segments are equal.
Therefore,
4 * 9 = x * 12
x = (4 * 9)/12
= 3
Therefore the correct answer s second option
x = 3
Drag the tiles to the correct boxes to complete the pairs. Not all tiles will be used.
Match each graph with the function it represents
Graph Function
A f(x) = x
B f(x) = x^2
C f(x) = x^3
D f(x) = √(x - 1)
E f(x) = 1/x
To match each graph with the function it represents, we need to consider the shape of the graph and the equation of the function.
Graph A: This graph is a straight line that passes through the origin and has a slope of 1.
This indicates that the function is linear and has the following equation:
f(x) = x
Graph B: This graph is a parabola that opens upwards and has its vertex at the origin.
This indicates that the function is quadratic and has the following equation:
f(x) = x^2
Graph C: This graph is a cubic function that opens upwards and has a point of inflection at the origin.
This indicates that the function has the following equation:
f(x) = x^3
Graph D: This graph is a square root function. It has a vertical asymptote at x = 1 and a horizontal asymptote at y = 1.
This indicates that the function has the following equation:
f(x) = √(x - 1)
Graph E: This graph is a reciprocal function. It has a vertical asymptote at x = 0 and a horizontal asymptote at y = 0.
This indicates that the function has the following equation:
f(x) = 1/x
Rewrite the following linear equation to slope form :y+2=7(2x-4)
Answer:
y = 14x -30
Step-by-step explanation:
The slope intercept form is:
y = mx + b,
Slope intercept form is useful for finding the slope and y intercept of a line, hence why it is called "slope intercept" because it is easy to see the slope and the y intercept of a line in this form. Since the slope denoted by m, and y intercept denoted by b are clearly given.
y + 2 = 7(2x - 4)
Distribute 7 across the parentheses by multiplying x and 2x and 4 by 7.
y+2 = 14x - 28
subtract 2 from both sides. This cancels the 2 on the left and moves it to the right, while keeping the equation balanced.
y+2 -2 = 14x - 28 -2
y = 14x - 30
y = 14x -30
As you can see our y = 14x -30 now looks like the point slope equation we had above. m = 14, and b = -30. This means the line goes up 14 for every single unit you move to the right, and intersects the y axis at (0, -30).
Please mark me brainliest.
A jar holds no more than 500 buttons. If 5 people bring 330 buttons each, how many jars are necessary to hold all of the buttons?
Answer:
We know
1 jar = 500 buttons
5 people bring 330 buttons EACH
We can find/solve by...
people x buttons = total buttons
total buttons / 500 = number of jars needed
So..
5 x 330 = 1650
1650 / 500 = 3.3
Your answer:
4 jars
Explanation
It's impossible to have 3.3 jars, so you must round up.
Step-by-step explanation:
The number of jar necessary to hold all buttons is 4 jars.
What is a unitary in math?Unitary method is a process by which we find the value of a single unit from the value of multiple units and the value of multiple units from the value of a single unit.
Given that
1 jar holds = 500 buttons
5 people = 330 buttons each
So,
Total buttons 5 people bring
=330*5
=1650 buttons
Now,
number of jars needed= total buttons/500
number of jars needed= 1650/500
number of jars needed= 3.3 jar
Hence, the number of jars needed is 4 jars
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Is the square root of 882252554089 a whole number or not?
Answer: It is a whole number.
Step-by-step explanation: As the square root of 882252554089 is equal to 939283, which has no decimal or fraction included, it is a whole number.
Which of the following represents the factorization of the trinomial below?
8x^2 + 10x+ 3
A. (4x+3)(2x + 3)
B. (4x+3)(2x+1)
C. (4x + 1)(2x + 3)
D. (4x+ 2)(3x + 1)
The correct factorization of the trinomial 8x^2 + 10x+ 3 is option B that is (4x+3)(2x+1).
What is factorization?
It means writing several factors usually of smaller or simpler objects of the same kind.
How to do factorization?
We have been given the following trinomial.
[tex]8x^{2} +10x+3[/tex]
We need 2 numbers in between which when multiplied gives 24 and when adds give 10. The required numbers are 6 and 4.
So,
[tex]8x^{2}[/tex]+6x+4x+3
2x(4x+3)+1(4x+3)
(2x+1)(4x+3)
Hence the required factorization is (2x+1)(4x+3).
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what is the value of x? please hurry.
Answer:
8
Step-by-step explanation:
Use the pythagorean theorem. The hypotenuse (c) is 10, and one of the sides, let's say (b), is 6. Therefore, we need to solve for a and plug and chug. Let's do that:
[tex]c^2 = a^2+b^2[/tex]
[tex]a = \sqrt{c^2-b^2}[/tex]
Now let's plug in what we know:
[tex]a = \sqrt{10^2-6^2} = \sqrt{64} = 8[/tex]
Therefore, a = x = 8
factor -24a^3b^3c^3 - 84a^4b^2c
The answer to your question is b.
Vhich solid figure has two parallel bases that are congruent polygons and
rectangular faces joining the bases?
A. Pyramid
B. Cone
c. Cylinder
D. Prism
Answer:
D
Step-by-step explanation:
Prism is the solid figure that has two parallel bases that are congruent polygons and rectangular faces joining the bases, i.e. option D.
What is prism?A prism is a 3D figure with two parallel bases and two congruent bases. The bases, which also have two of the faces, can be any polygon and are congruent. The other faces are rectangles and joins bases. A prism is named according to the shape of its bases. i.e. Triangular prism, Rectangular prism, etc.
We have,
A solid figure with two parallel and congruent bases.
Now,
From the above mentioned definition,
i.e.
A prism is a 3D figure with two parallel bases and two congruent bases. The bases, which also have two of the faces, can be any polygon and are congruent. The other faces are rectangles and joins bases.
So,
It is clear that the given solid figure is of prism.
Hence, we can say that the Prism is the solid figure that has two parallel bases that are congruent polygons and rectangular faces joining the bases, i.e. option D.
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What is 9.18 × 103 in standard form?
Answer:
9.179999999999999e+103
Answer:
C) 7,900
Step-by-step explanation:
Peter can paint a room in 5 hours, Paul can paint a room in 6 hours, Neil can paint a room in 7 1/2 hours and Mary can paint a room in 3 3/4 hours.
Which two painters above can team up to paint a whole room in 3 hours?
Write and solve a Rational Equation that shows you are correct. Please show your work.
paul and mary
peter and mary
peter and paul
Answer:
Peter and Neil
Step-by-step explanation:
Given rates of work:
Peter = 5 hours / room
Paul = 6 hours / room
Neil = 7.5 hours / room
Mary = 3.75 hours / room
Recall the formula for combined rate for two individuals A & B is given as
Combined rate = (A's rate x B's rate) / (A's rate + B's rate)
In our case , the combined rate is given to be 3 hours, so we must find a combination of rate A and rate B that will give us 3 hours.
If you try all the combinations in the above formula, we will find that if we substitute Peter's and Neil's rates into the formula, we will get exactly 3 hours.
Combined rate for Peter and Neil
= (Peter's rate x Neil's rate) / (Peter's rate + Neil's rate)
= (5 x 7.5) / (5+7.5) = 3 hours to complete 1 room
No other combination gives exactly 3 hours.