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2 years ago

What are the prime factors of 28?

Mathematics

2 answers:

koban [17]2 years ago

5 0

Answer:

2 and 7 are the prime numbers.

Step-by-step explanation:

Tju [1.3M]2 years ago

5 0

Answer:

28=2 x 2 x7

Step-by-step explanation:

draw a prime factor tree

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Which expression is equal to 3(56)? 3(50 + 6) 3(50) + (6) 5(30 + 6) 5(30) + 5(6)

Mariana [72]

Answer:3(50+6)

Step-by-step explanation:

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2 years ago

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The half-life of a certain tranquilizer in the bloodstream is 22 hours. How long will it take for the drug to decay to 90% of

nasty-shy [4]

Answer:

It will take approximately 3.34 hours for the drug to decay to 90% of the original dosage

Step-by-step explanation:

As suggested, we use the formula for exponential decay:

$A(t)=A_0\,e^{-k\,t}$

From the given information, the half life of the drug in blood id 22 hours, so that means that it takes that number of hours to go from the initial value $A_0$ , to a final value equal to $A_0/2$ . Using this information we can find the decay rate "k" by solving for this parameter in the formula, and using the natural log function to bring the exponent down:

$A(t)=A_0\,e^{-k\,t}\\\frac{A_0}{2} =A_0\,e^{-k\,*22}\\\frac{A_0}{A_0*2} =e^{-k\,*22}\\\frac{1}{2} =e^{-k\,*22}\\ln(\frac{1}{2})=-k\,*22\\ k=-\frac{ln(\frac{1}{2})}{22} \\k=0.0315$

Now we use this value for the decay rate "k" to calculate how long it would take to decay to 90% of the original dose;

$A(t)=A_0\,e^{-0.0315\,t}\\0.9*A_0} =A_0\,e^{-0.0315\,t}\\\frac{0.9*A_0}{A_0} =e^{-0.0315\,t}\\0.9 =e^{-0.0315\,t}\\ln(0.9)=-0.0315\,t\\ t=-\frac{ln(0.9)}{0.0315} \\t=3.3447\,hours$

7 0

2 years ago

6. In a toy factory, 200 wooden closed cylinders of diameter 35 mm and height 7 cm have to be painted. What is the total surface

Pachacha [2.7K]

Answer:

6) About 19,244.75 square centimeters.

7) About 4895 containers.

Step-by-step explanation:

Question 6)

We need to paint 200 wooden closed cylinders of diameter 35 mm and height 7 cm. And we want to find the total surface area that needs to be painted.

First, since the diameter is 35 mm, this is equivalent to 3.5 cm.

The radius is half the diameter, so the radius of each cylinder is 1.75 cm.

Recall that the surface area of a cylinder is given by the formula:

$\displaystyle \text{SA}=2\pi r^2+ 2\pi rh$

Where r is the radius and h is the height.

Therefore, the surface area of a single cylinder will be:

$\displasytyle \text{SA}=2(3.142)(1.75)^2+2(3.142)(1.75)(7) = 96.22375\text{ cm}^2$

Then the total surface area for 200 cylinders will be:

$\displaystyle \text{SA}_{\text{total}}=200(96.22375)=19244.75\text{ cm}^2$

Question 7)

We know that the tank has a diameter of 2.4 m and a height of 6.4 m.

Since its diamter is 2.4 m, then its radius is 1.2 m.

Find the total volume of the tank. The volume for a cylinder is given by:

$\displaystyle V=\pi r^2h$

Since r = 1.2 and h = 6.4:

$\displaystyle V=(3.142)(1.2)^2(6.4)=28.956672\text{ m}^3$

Each container has a base radius of 8.2 cm and a height of 28 cm.

So, the radius of each container is 0.082 m and the height is 0.28 m.

Then the volume of each container is:

$\displaystyle V=(3.142)(0.082)^2(0.28)=0.005915506\text{ m}^3$

Then to find the number of containers that can be filled by the tank, we can divide the two values. Hence:

$\displaystyle C=\frac{28.956672}{0.005915506}=4895.045466\approx 4895$

Thus, approximately 4895 containers can be filled.

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2 years ago

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Which set is closed under the operation multiplication?

oee [108]

I have another set of choices here:

A. {0.5, 1, 2}

B. {1, 2, 4}

C. {1, 2, 3, 4, 5}

D. {0}

If you multiply two numbers from a closed set the answer is in the set.
So A is not closed because 2 x 2 = 4 which isn't in the set. Only 0.5, 1, and 2 are in set A. 

Try multiplying the largest numbers in sets B, C, and D by themselves. You will soon discover the closed set.

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2 years ago

What is the sum of the two vectors (-1,-4) and (3,5)

o-na [289]

Answer:

Step-by-step explanation:

$a(-1, -4)\\b(3, 5)\\a + b(2, 1)$

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2 years ago

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