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Amiraneli [1.4K]
3 years ago
15

A certain compound has a half-life of four days. Write and use an exponential decay function to find the amount of compound rema

ining from a 75-ounce sample after three weeks .
Mathematics
1 answer:
dimaraw [331]3 years ago
4 0

Answer:

1.97 ounces

Step-by-step explanation:

-The exponential decay function is given by the formula:

P_t=P_oe^{-rt}\\\\

Given that the half-life is 4 days, we can substitute in the formula to solve the rate of decay for a single half-life:

P_t=P_oe^{rt}\\\\P_t=0.5P_o\\\\\therefore 0.5=e^{-4r}\\\\-4r=In(0.5)\\\\r=0.17329

#Since, 1 week has 7 days, 3 weeks is a 21-day period, thus, t=21.

#We substitute and solve for the amount remaining after 21days of decay:

P_t=P_oe^{-rt}\\\\=75e^{-21\times 0.17329}\\\\=1.97072\\\\\approx1.97 \ oz

Hence, the amount remaining after 3 weeks of decays is approximately 1.97 ounces

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3 years ago
In an anthropology class there are 77 anthropology majors and 1414 non-anthropology majors. 55 students are randomly selected to
Nata [24]

Answer:

P = 0.9989

Step-by-step explanation:

In order to do this, I will use the following numbers to make the calculations easier. In this case, We'll say that we have 7 majors and 14 non majors anthopology to present a topic.

This means that in the class we have 21 students.

Now, we choose 5 of them, and we want to know the probability that 1 of them is non major.

First, we need to calculate the number of ways we can select the students in all cases, and then, the probability.

First, we'll use the combination formula, to calculate the number of ways we can select the 5 students out of the 21. We use combination, because it does not matter the order that the students are selected.

C = m! / n!(m - n)!

Where:

m: number of students

n: number of selected students out of m.

With this expression we will calculate first, how many ways we can choose the 5 students out of 21:

C1 = 21! / 5!(21-5)! = 20,349

Now let's calculate the number of ways you can get the all 5 students are non majors:

C2 = 14! / 5!(14 - 5)! = 2002

Now we need to know the number of ways we can get 4 non majors and 1 major:

C3 = C3' * C3''

C3' represents the number of ways we can get 4 non majors and the C3'' represents the number of ways we can get 1 major.

C3' = 14! / 4!(14 - 4)! = 1,001

C3'' = 7! / 1!(7 - 1)! = 7

C3 = 1001 * 7 = 7,007 ways to get 4 non majors and 1 major

Now the way to get 3 non majors and 2 majors, we do the same thing we do to get 4 non majors and 1 major, but changing the numbers. Then the way to get 2 non majors and 3 majors, and finally 1 non major and 4 majors:

3 non majors and 2 majors:

C4 = C4' * C4'' = [14! / 3!(14 - 3)!] * [7! / 2!(7 - 2)!] = 7,644

2 non majors and 3 majors:

C5 = C5' * C5'' = [14! / 2!(14 - 2)!] * [7! / 3!(7 - 3)!] = 3,185

1 non major and 4 majors:

C6 = C6' * C6'' = [14! / 1!(14 - 1)!] * [7! / 4!(7 - 4)!] = 490

Finally to know the probability of getting 1 out of the 5 to be non major, we have to sum all the previous results, and divide them by the ways we can choose the 5 students (C1):

P = 2,002 + 7,007 + 7,644 + 3,185 + 490 / 20,349

P = 0.9989

5 0
3 years ago
In a wood there are 420 silver birch trees, 160 oak trees and 300 wild berry trees. what percentage of the trees are oak trees?
Alex73 [517]
I would be happy to help!
First you need to find the total amount of trees by adding up all of the different trees:
420+160+300=880
Next you need to divide the amount of oak trees by the amount of trees in the woods:
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3 years ago
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ivolga24 [154]

Answer:

The number of hours did Sarah practice more than Leilani is \dfrac{11}{40}  hours  .

Step-by-step explanation:

Given as :

The time for which Leilani practiced piano = \dfrac{3}{5} hours

The time for which Sarah practiced piano = \dfrac{7}{8} hours

Let the number of hours did Sarah practice more than Leilani = T hours

<u>Now, According to question</u>

The number of hours did Sarah practice more than Leilani = \dfrac{7}{8} hours -  \dfrac{3}{5} hours

Or, T =  \dfrac{35-24}{40} hours

Or, T =  \dfrac{11}{40} hours

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