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nalin [4]
2 years ago
10

Which of the following situations could be modeled by an exponential function?

Mathematics
1 answer:
Sauron [17]2 years ago
3 0

Answer: Option D.

Step-by-step explanation:

An exponential function is something like:

f(x) = A*(r)^x

Where:

A = initial amount.

r = rate of growth

x = variable.

This type of function is used to describe situations like "you have A dollars, and it increases by 30% each week"

or:

"There is a population of A animals, and it doubles each year"

Let's analyze briefly all the given options and see which one is an exponential function.

A) The water level of a tank decreases by 5 gallons every day.

This is a linear relation, if W is the initial amount of water, and x is the number of days, then the water level of the tank after x days is:

y = W - 5 gal*x

B) The amount of money collected by a charity increases by $5,000 each year.

The amount collected increases $5000 each year.

Then if in year 1 they collected A.

in year 2 they collected A + $5000

in year 3 they collected A + 2*$5000

We already can see the pattern, this is a linear relation:

in year X they colected A + (X - 1)*$5000

C) A tree was 10 feet tall when purchased and grows at a rate of 2 feet per year.

if y is the height of the tree, and x is the number of years, this can be written as:

y = 10ft + x*2ft

Again, a linear relation.

D) The number of people in a stadium is decreasing at a rate of 45% every 10 minutes.

Let's define x as each "lapse" of 10 minutes that passes.

If N is the initial number of people in te stadium, then after 10 minutes the number of people is = N*(1 - 45%/100%) = N*(1 - 0.45) = N*0.55

After another 10 minutes, the population decreases again.

N*0.55*(1 - 45%/100%) = N*0.55*0.55 = N*0.55^2

We can see the pattern here, this can be written as

People(x) = N*(0.55)^x

This is an exponential function.

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Suppose that a fast food restaurant decides to survey its customers to gauge interest in a breakfast menu. After surveying multi
Harlamova29_29 [7]

Answer:

ME= \frac{Width}{2}=\frac{0.078}{2}=0.039

\hat p =0.688+0.039=0.727

\hat p =0.766-0.039=0.727

Step-by-step explanation:

Assuming that the confidence interval is (0.688; 0.766)

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".  

The margin of error is the range of values below and above the sample statistic in a confidence interval.  

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".  

The population proportion have the following distribution  

p \sim N(p,\sqrt{\frac{p(1-p)}{n}})  

The confidence interval would be given by this formula  

\hat p \pm z_{\alpha/2} \sqrt{\frac{\hat p(1-\hat p)}{n}}  

For the 95% confidence interval the value of \alpha=1-0.95=0.05 and \alpha/2=0.025, with that value we can find the quantile required for the interval in the normal standard distribution.  

z_{\alpha/2}=1.96  

Use the confidence interval to find the point estimate and margin of error for the proportion

The margin of error is given by :

Me=z_{\alpha/2} \sqrt{\frac{\hat p(1-\hat p)}{n}}

And for our case we can find the width of the confidence interval like this:

Width =0.766-0.688=0.078

And the estimation for the margin of error would be given by:

ME= \frac{Width}{2}=\frac{0.078}{2}=0.039

Now we can find th point of estimate adding the margin of error to the lower limit of the interval or subtracting the margin of error to the upper limit, like this:

\hat p =0.688+0.039=0.727

\hat p =0.766-0.039=0.727

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Answer:

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Step-by-step explanation:

For this problem we will be using trigonometry :

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Answer:

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Step-by-step explanation:

In three minutes the water volume has decreased by 2 gallons (7 less 5 is 2).  The unit rate of decrease of the amount of water in the tank is thus:

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