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3 years ago

You collect a total of $75 in donations from three people. The three donations are in the ratio 4 : 4 : 7.

1 answer:

7 0

75 in donations...ratio of 4:4:7....added (4+4+7) = 15

4/15(75) = 300/15 = 20 <==
4/15(75) = 300/15 = 20 <==
7/15(75) = 525/15 = 35 <==

the smaller donation is $ 20
the larger donation is $ 15 greater then the smaller donation

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you have a piece of wood that is 72 inches long u cut the wood into three pieces the second piece is 6 inches longer than the fi

tangare [24]

Let

x---------> the length of the first piece

y---------> the length of the second piece

z---------> the length of the third piece

we know that

x+y+z=72 -------> equation 1

y=x+6 -----> solve for x

x=y-6 -------> equation 2

z=6+y -------> equation 3

substitute equation 2 and equation 3 in equation 1

[y-6]+y+[6+y]=72

3y=72

y=(72/3)=24 in

Find the value of x

x=y-6 -------> equation 2

x=24-6=18 in

Find the value of z

z=6+y -------> equation 3

z=6+24=30 in

therefore

the answer is

the length of the first piece is 18 in

the length of the second piece 24 in

the length of the third piece is 30 in

7 0

3 years ago

In a very survey of 60 student,60 study botany 50 study zoology and 48 studied biology.if 38 study all,how many study zoology al

BabaBlast [244]

Answer:

12 study zoology alone and 0 study none

6 0

3 years ago

Use the linear combination method to solve the system of equations. Explain each step of your solution. 2x-3y=13 4x-y=-9

Tems11 [23]

2x -3y = 13

4x -y = -9

Multiply the second equation by -3 to make the coefficient of Y opposite the first equation.

4x -y = -9 x -3 = -12x + 3y = 27

Now add this to the first equation:

2x -12x = -10x

-3y +3y = 0

13 +27 = 40

Now you have :

-10x = 40

Divide each side by -10:

x = 40 / -10

x = -4

Now you have a value for x, replace that into the first equation and solve for y:

2(-4) - 3y = 13

-8 - 3y = 13

Add 8 to both sides:

-3y = 21

Divide both sides by -3:

y = 21/-3

y = -7

Now you have X = -4 and y = -7

(-4,-7)

3 0

3 years ago

A survey of 700 adults from a certain region asked, "What do you buy from your mobile device?" The results indicated that 59%

Kryger [21]

Answer:

a) the test statistic z = 1.891

the null hypothesis accepted at 95% level of significance

b) the critical values of 95% level of significance is zα =1.96

c) 95% of confidence intervals are (0.523 ,0.596)

Step-by-step explanation:

A survey of 700 adults from a certain region

Given sample sizes $n_{1} = 400 and n_{2} = 300$

Proportion of mean $p_{1} = \frac{236}{400} = 0.59 and p_{2} = \frac{156}{300} = 0.52$

Null hypothesis H0 : assume that there is no significant difference between males and women reported they buy clothing from their mobile device

p1 = p2

Alternative hypothesis H1:- p1 ≠ p2

a) The test statistic is

$Z = \frac{p_{1} -p_{2} }{\sqrt{pq(\frac{1}{n_{1} }+\frac{1}{n_{2} )} } }$

where $p = \frac{n_{1}p_{1} +n_{2}p_{2} }{n_{1}+n_{2}}= \frac{400X0.59+300X0.52}{700}$

on calculation we get p = 0.56

now q =1-p = 1-0.56=0.44

$Z = \frac{p_{1} -p_{2} }{\sqrt{pq(\frac{1}{n_{1} }+\frac{1}{n_{2} )} } }\\ =\frac{0.56-0.52}{\sqrt{0.56X0.44}(\frac{1}{400}+\frac{1}{300} }$

after calculation we get z = 1.891

b) The critical value at 95% confidence interval zα = 1.96 (from z-table)

The calculated z- value < the tabulated value

therefore the null hypothesis accepted

conclusion:-

assume that there is no significant difference between males and women reported they buy clothing from their mobile device

p1 = p2

c) 95% confidence intervals

The confidence intervals are P± 1.96(√PQ/n)

we know that = $p = \frac{n_{1}p_{1} +n_{2}p_{2} }{n_{1}+n_{2}}= \frac{400X0.59+300X0.52}{700}$

after calculation we get P = 0.56 and Q =1-P =0.44

Confidence intervals are ( P- 1.96(√PQ/n), P+ 1.96(√PQ/n))

now substitute values , we get

( 0.56- 1.96(√0.56X0.44/700), 0.56+ 1.96(0.56X0.44/700))

on simplification we get (0.523 ,0.596)

Therefore the population proportion (0.56) lies in between the 95% of confidence intervals (0.523 ,0.596)

3 0

3 years ago

The base of an aquarium with given volume V is made of slate and the sides are made of glass. If slate costs five times as much

Y_Kistochka [10]

Answer:

x = ∛ 2*V/5

y = ∛ 2*V/5

h = V/ ∛ 4*V²/25

Step-by-step explanation:

Dimensions of the aquarium base is x*y

We call c₁ cost per unit area of the sides, then cost per unit area of slate is equal 5c₁.

let call h the height of the aquarium then volume of the aquarium is:

V = x*y*h where h = V / x*y

As the base is a rectangular one there are 2 sides x*h . and 2 sides y*h

According to this:

Ct (cost of aquarium ) = cost of the base + cost of the sides

cₐ ( cost of the base) = 5*c₁*x*y

c₆ (cost of the sides ) = c₁*2*x*h + c₁*2*y*h

C(t) = 5*c₁*x*y +2* c₁*x* V/x*y + 2* c₁*y* V/x*y or

C(t) = 5*c₁*x*y + 2*c₁*V/y *2*c₁* V/x

Taking partial derivatives en x and y we have:

C´(x) = 5*c₁*y - 2*c₁*V/x²

C´(y) = 5*c₁*x - 2*c₁*V/y²

C´(x) = C´(y) ⇒ 5*c₁*y - 2*c₁*V/x² = 5*c₁*x - 2*c₁*V/y²

or 5*y - 2*V/x² = 5*x - 2*V/y²

(5*y*x² - 2*V)/x² = ( 5*y²x - 2*V) /y²

(5*y*x² - 2*V)*y² = ( 5*y²x - 2*V)*x²

5*y³*x² - 2*V*y² = 5*y²x³ - 2*V*x²

5*y³*x² - 5*y²x³ = 2*V * ( y² - x²)

by symmetry x = y

Then using x = y and plugging that value on the derivatives

C´(x) = 5*c₁*y - 2*c₁*V/x²

C´(x) = 5*c₁*x - 2*c₁*V/x²

C´(x) = 0 ⇒ 5*c₁*x - 2*c₁*V/x² = 0

5*x - 2*V/x² = 0 ⇒ 5*x³ - 2*V = 0 ⇒ 5*x³ = 2*V ⇒ x³ = 2*V/5

x = ∛ 2*V/5 and y = ∛ 2*V/5 and h = V/ x*y h = V/ ∛ 4*V²/25

7 0

3 years ago