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2 years ago

How do I subtract fractions? Please explain step by step to get marked!

Mathematics

1 answer:

Mashutka [201]2 years ago

7 0

Answer:

Explained below :)

(I tried my best, sorry if it doesn't make sense.)

Step-by-step explanation:

Example: 1/4 - 1/8= ?

1: Find the common denominator (bottom number)

2: If the common denominator is 8 then you multiply 1/4 by 2/2 to get the denominator of 8. If you needed then you can multiply the other fraction to get the same denominator.

3: Once you get multiply that then you get 2/8 -1/8.

4: Subtract the numerator (top number) 1

5: Keep the numerator (8)

6: Your answer would be 1/8

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Suppose that 12% of test scores for the unit 1 test were above 85 and 8% were below 70. Assuming a normal

Doss [256]

Answer:

Mean = 78.2

Standard deviation = 5.8

Step-by-step explanation:

Mathematically z-score;

= (x-mean)/SD

From the question;

12% of test scores were above 85

Thus;

P( x > 85) = 12%

P(x > 85) = 0.12

Now let’s get the z-score that has a probability of 0.12

This can be obtained from the standard normal distribution table and it is = 1.175

Thus;

1.175 = (85 - mean)/SD

let’s call the mean a and the SD b

1.175 = (85-a)/b

1.175b = 85 - a

a = 85 - 1.175b ••••••••(i)

Secondly 8% of scores were below 70

Let’s find the z-score corresponding to this proportion;

We use the standard normal distribution table as usual;

P( x < 70) = 0.08

z-score = -1.405

Thus;

-1.405 =( 70-a)/b

-1.405b = 70-a

a = 70 + 1.405b ••••••(ii)

Equate the two a

70 + 1.405b = 85 - 1.175b

85 -70 = 1.405b + 1.175b

15 = 2.58b

b = 15/2.58

b = 5.81

a = 70 + 1.405b

a = 70 + 1.405(5.81)

a = 78.16

So mean = 78.2 and Standard deviation is 5.8

4 0

3 years ago

A rectangular box is to have a square base and a volume of 12 ft3. If the material for the base costs $0.17/ft2, the material fo

katen-ka-za [31]

Answer:

(a)Length =2 feet

(b)Width =2 feet

(c)Height=3 feet

Step-by-step explanation:

Let the dimensions of the box be x, y and z

The rectangular box has a square base.

Therefore, Volume of the box $V=x^2z$

Volume of the box $=12 ft^3\\$

$Therefore, x^2z=12\\z=\frac{12}{x^2}$

The material for the base costs $\$0.17/ft^2$ , the material for the sides costs $\$0.10/ft^2$ , and the material for the top costs $\$0.13/ft^2$ .

Area of the base $=x^2$

Cost of the Base $=\$0.17x^2$

Area of the sides $=4xz$

Cost of the sides= $=\$0.10(4xz)$

Area of the Top $=x^2$

Cost of the Base $=\$0.13x^2$

Total Cost, $C(x,z) =0.17x^2+0.13x^2+0.10(4xz)$

Substituting $z=\frac{12}{x^2}$

$C(x) =0.17x^2+0.13x^2+0.10(4x)(\frac{12}{x^2})\\C(x)=0.3x^2+\frac{4.8}{x} \\C(x)=\dfrac{0.3x^3+4.8}{x}$

To minimize C(x), we solve for the derivative and obtain its critical point

$C'(x)=\dfrac{0.6x^3-4.8}{x^2}\\Setting \:C'(x)=0\\0.6x^3-4.8=0\\0.6x^3=4.8\\x^3=4.8\div 0.6\\x^3=8\\x=\sqrt[3]{8}=2$

Recall: $z=\frac{12}{x^2}=\frac{12}{2^2}=3\\$

Therefore, the dimensions that minimizes the cost of the box are:

(a)Length =2 feet

(b)Width =2 feet

(c)Height=3 feet

7 0

3 years ago

<img src="https://tex.z-dn.net/?f=2x%28x%20-%202%29%5E%7B2%7D%20%20%2B%203x%28x%20%2B%203%29%5E%7B2%7D%20%20-%20x%5E%7B2%7D%20%2

Ratling [72]

= x·[2(x²- 4x + 4) + 3(x² + 6x + 9) - x² + 5x]

= x(2x² - 8x + 8 + 3x² + 18x + 27 - x² + 5x)

= x(4x² + 15x + 35)

5 0

3 years ago

A pentagonal prism has a height of 9 feet, and each base edge is 3 feet. Find the volume. Round your answer to the nearest hundr

OLga [1]

Height of the pentagon = 9 ft

Edge of base = 3 ft

$area of pentagon = \frac{s^{2}n}{4 tan\left ( \frac{180}{n} \right )}$

s is the length of any side = 3

n is the number of sides = 5

tan is the tangent function calculated in degrees

$\\ \\\\area of pentagon = \frac{3^{2}(5)}{4 tan\left ( \frac{180}{5} \right )}\\\\\\area of pentagon = \frac{9(5)}{4 tan\left ( 36 \right )}\\\\area of pentagon = \frac{45}{4 ( 0.7265 )}\\\\area of pentagon = \frac{45}{2.906}\\\\area of pentagon = 15.4852$

Volume of the pentagon = area of base (height )

Volume of the pentagon = 15.4852 (9)

Volume of the pentagon = 139.366

Volume of the pentagon = 139.37 cu.ft

5 0

3 years ago

Read 2 more answers

I need to know all the answers

Scilla [17]

Answer: that’s all it says.

Step-by-step explanation:

8 0

3 years ago