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3 years ago

Um help again. i’m terrible with math so an answer would really help thxs :)

Mathematics

1 answer:

Leni [432]3 years ago

4 0

Answer:

Step-by-step explanation:

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The ratio of nonfiction books to fiction books in a library is 105 to 189. Which statement describes this relationship?

kolezko [41]

Answer: A)There are 5 nonfiction books for every 9 fiction books in the library.

Step-by-step explanation: If you do the math you realize that there are clearly less nonfiction books than fiction books.

105/5=21 and after 21*9 lines up and to check your work than

5*21=105 and 9*21=189 it is not B because the smaller number 105 is in front of the ratio 105:189 and 5:9

7 0

4 years ago

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Initially 100 milligrams of a radioactive substance was present. After 6 hours the mass had decreased by 3%. If the rate of deca

Hitman42 [59]

Answer:

The half-life of the radioactive substance is 135.9 hours.

Step-by-step explanation:

The rate of decay is proportional to the amount of the substance present at time t

This means that the amount of the substance can be modeled by the following differential equation:

$\frac{dQ}{dt} = -rt$

Which has the following solution:

$Q(t) = Q(0)e^{-rt}$

In which Q(t) is the amount after t hours, Q(0) is the initial amount and r is the decay rate.

After 6 hours the mass had decreased by 3%.

This means that $Q(6) = (1-0.03)Q(0) = 0.97Q(0)$ . We use this to find r.

$Q(t) = Q(0)e^{-rt}$

$0.97Q(0) = Q(0)e^{-6r}$

$e^{-6r} = 0.97$

$\ln{e^{-6r}} = \ln{0.97}$

$-6r = \ln{0.97}$

$r = -\frac{\ln{0.97}}{6}$

$r = 0.0051$

$Q(t) = Q(0)e^{-0.0051t}$

Determine the half-life of the radioactive substance.

This is t for which Q(t) = 0.5Q(0). So

$Q(t) = Q(0)e^{-0.0051t}$

$0.5Q(0) = Q(0)e^{-0.0051t}$

$e^{-0.0051t} = 0.5$

$\ln{e^{-0.0051t}} = \ln{0.5}$

$-0.0051t = \ln{0.5}$

$t = -\frac{\ln{0.5}}{0.0051}$

$t = 135.9$

The half-life of the radioactive substance is 135.9 hours.

6 0

3 years ago

Did I do this right?

Rasek [7]

Answer:

Yea u did......

Step-by-step explanation:

you did right because all the steps are right

5 0

3 years ago

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Y=2x-1 is the point with coordinates (5,11) on the line y=ex-1? true or false

Arada [10]

Answer:

False

Step-by-step explanation:

Here, we want to check if the point given is on the line

To get this, we simply proceed to substitute the point given into the equation

Thus, we have;

11 = 2(5) - 1

11 = 10-1

11 is not equal to 9

Since these are not equal, then the point is not on the line

3 0

3 years ago

What is the square root 47 to the nearest tenth

Damm [24]

6.9 is your answer for your question.

4 0

4 years ago

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