The triangle below has a perimeter of 27 cm.

A news item is spreading by word of mouth through a population of size 12,000 people. After t days, the number of people (in tho

Lilit [14]

Answer:

a) 2.303

b) $f'(t)=\frac{432e^{-0.48t}}{(1+75e^{-0.48t})^{2}}$

c) 1.3609

e) $\frac{dy}{dx}=0.04y(12-y)$

f) 4.5 thousand people(smaller)

7.5 thousand people (larger)

e) t=7.93 days (smaller)

t=10.06 days (larger)

g) 1.44

Step-by-step explanation:

The given function is $y=f(t)=\frac{12}{1+75e^{-0.48t}}$

To find how many thousand people have heard the news after 6 days, we substitute to get:

$f(6)=\frac{12}{1+75e^{-0.48*6}}=2.303$ thousands.

b) We rewrite to get: $f(t)=12(1+75e^{-0.48t})^{-1}$

We differentiate using the chain rule to obtain:

$f'(t)=-12(1+75e^{-0.48t})^{-2}\cdot 75e^{-0.48t}\cdot -0.48$

This simplifies to:

$f'(t)=432e^{-0.48t}(1+75e^{-0.48t})^{-2}$

We rewrite as positive index to get:

$f'(t)=\frac{432e^{-0.48t}}{(1+75e^{-0.48t})^{2}}$

c) To find the rate at which the news is spreading after 8 days, we substitute t=8 into $f'(t)=\frac{432e^{-0.48t}}{(1+75e^{-0.48t})^{2}}$ to get:

$f'(8)=\frac{432e^{-0.48\cdot 8}}{(1+75e^{-0.48\cdot 8})^{2}}=1.3609$

d) The solution to the logistic differential equation:

$\frac{dy}{dt}=ky(M-y)$

is

$y=\frac{M}{1+be^{-Mkt}}$

By comparison, M=12, and $Mk=0.48$

$12k=0.48\\k=0.04$

The differential equation is:

$\frac{dy}{dx}=0.04y(12-y)$

e) To how many people have heard the news when its rate of spread is 1.35 thousand per day, we equate the differential equation to 1.35 and so for t first.

$\frac{432e^{-0.48t}}{(1+75e^{-0.48t})^{2}}=1.35$

This gives us: t=10.06 ot t=7.93

We substitute the times into the function to get:

$f(7.93)=\frac{12}{1+75e^{-0.48\cdot7.93}}$ =4.5 thousand: smaller value

$f(10.06)=\frac{12}{1+75e^{-0.48\cdot10.06}}=7.5$ thousand: Larger value

f) The two times that the news is spreading at rate 1.35 thousand people per day are:

$t=7.93$ days: Smaller value

$t=10.06$ : Larger value

g) To find the fastest rate at which the news spread we take the second derivative and equate it to zero.

$f''(t)=0$

This corresponds to where the horizontal line is tangent to

$f'(t)=\frac{432e^{-0.48t}}{(1+75e^{-0.48t})^{2}}$

From the graph the point of tangency is:

(8.99,1.44)

Therefore the fastest rate at which the news spread is 1.44

7 0

3 years ago

Name the ray in the figure

Pavlova-9 [17]

the answer is m to p

5 0

4 years ago

Read 2 more answers

Question 10. Simplify the expression. (x^2 - 9)/(x^2 + 2x - 15)

krek1111 [17]

So the right ans is of option B.

Look at the attached picture ⤴

Hope it will help u...

3 0

3 years ago

Rewrite in simplest terms: 5(0.9m+0.5)-3(0.4m+0.7)

hram777 [196]

Answer:

3.3m+1.4

Step-by-step explanation:

Multiply 5 and 0.9m

Multiply 5 and 0.5

5 times 0.9m is 4.5m

5 times 0.5 is 2.5

Multiply -3 and 0.4m

Multiply -3 and 0.7

-3 times 0.4m is -1.2m

-3 times -.7 is -2.1

4.5m+ 2.5 -1.2m-2.1

Which is 3.3m+1.4

Hope this helps!

3 0

3 years ago

What proportion of US women have a height greater than 69.5 inches?

kiruha [24]

Using the Normal distribution, it is found that 0.0359 = 3.59% of US women have a height greater than 69.5 inches.

In a normal distribution with mean $\mu$ and standard deviation $\sigma$ , the z-score of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

It measures how many standard deviations the measure is from the mean.

After finding the z-score, we look at the z-score table and find the p-value associated with this z-score, which is the percentile of X.

US women’s heights are normally distributed with mean 65 inches and standard deviation 2.5 inches, hence $\mu = 65, \sigma = 2.5$ .

The proportion of US women that have a height greater than 69.5 inches is 1 subtracted by the p-value of Z when X = 69.5, hence:

$Z = \frac{X - \mu}{\sigma}$

$Z = \frac{69.5 - 65}{2.5}$

$Z = 1.8$

$Z = 1.8$ has a p-value of 0.9641.

1 - 0.9641 = 0.0359

0.0359 = 3.59% of US women have a height greater than 69.5 inches.

You can learn more about the Normal distribution at brainly.com/question/24663213

3 0

3 years ago