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lisabon 2012 [21]

3 years ago

13

1. Amelia can do 5 sit-ups. Her goal is to increase to 50 sit-ups by adding 5 more sit-ups to her training schedule each week. A

melia wants to know how many weeks it will take to reach her goal of 50 sit-ups. Part A Is Amelia's training goal best described by an equation or an inequality? Explain.

1 answer:

Olegator [25]3 years ago

4 0

Answer:

(i) Equation

(ii) 10 weeks

Step-by-step explanation:

The scenario is an equation and not an inequality , this is because the number of sit - ups Amelia planned to do is specific , which is 50 , had it been the question used the word like at least , at most 50 , it would have been an inequality.

The question is an example of Arithmetic sequence

From the statement ;

The first term = 5

The common difference = 5 ( since Amelia planned to add 5 more sit - ups to her training schedule each week )

The formula for the nth term of an Arithmetic sequence is given by :

$t_{n}$ = a + (n- 1 )d

$t_{n}$ = 50

a = 5

d = 5

n = ?

substituting the values , we have

50 = 5 + (n - 1 ) x 5

50 = 5 + 5n - 5

50 = 5n

n = 10

Therefore , it will take Amelia 10 weeks to reach her goal of 50 sit - ups

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SAT scores are normed so that, in any year, the mean of the verbal or math test should be 500 and the standard deviation 100. as

vovangra [49]

Answer:

a) $P(X>625)=P(\frac{X-\mu}{\sigma}>\frac{625-\mu}{\sigma})=P(Z>\frac{625-500}{100})=P(Z>1.25)$

$P(Z>1.25)=1-P(Z$

b) $P(400$

$P(-1$

$P(-1$

c) $z=-0.842$

And if we solve for a we got

$a=500 -0.842*100=415.8$

So the value of height that separates the bottom 20% of data from the top 80% is 415.8.

Step-by-step explanation:

Previous concepts

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 Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".

Part a

Let X the random variable that represent the SAT scores of a population, and for this case we know the distribution for X is given by:

$X \sim N(500,100)$

Where $\mu=500$ and $\sigma=100$

We are interested on this probability

$P(X>625)$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

If we apply this formula to our probability we got this:

$P(X>625)=P(\frac{X-\mu}{\sigma}>\frac{625-\mu}{\sigma})=P(Z>\frac{625-500}{100})=P(Z>1.25)$

And we can find this probability using the complement rule and with the normal standard table or excel:

$P(Z>1.25)=1-P(Z$

Part b

We are interested on this probability

$P(400$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

If we apply this formula to our probability we got this:

$P(400$

And we can find this probability with this difference:

$P(-1$

And in order to find these probabilities we can find tables for the normal standard distribution, excel or a calculator.

$P(-1$

Part c

For this part we want to find a value a, such that we satisfy this condition:

$P(X>a)=0.8$ (a)

$P(X$ (b)

Both conditions are equivalent on this case. We can use the z score again in order to find the value a.

As we can see on the figure attached the z value that satisfy the condition with 0.2 of the area on the left and 0.8 of the area on the right it's z=-0.842. On this case P(Z<-0.842)=0.2 and P(Z>-0.842)=0.8

If we use condition (b) from previous we have this:

$P(X$

$P(z$

But we know which value of z satisfy the previous equation so then we can do this:

$z=-0.842$

And if we solve for a we got

$a=500 -0.842*100=415.8$

So the value of height that separates the bottom 20% of data from the top 80% is 415.8.

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Answer:

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Step-by-step explanation:

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When a decimal is to the left of given number, then we need to move the decimal to right such that the number gets between 1 and 10. Then, we multiply the number by negative power of 10 that many times, we moved the decimal to right.

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Answer:

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Step-by-step explanation:

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