Data Properties - Algebra II

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Question

There exists a function f(x) = 3_x_ + 2 for x = 2, 3, 4, 5, and 6. What is the average value of the function?

Answer

First we need to find the values of the function: f(2) = 3 * 2 + 2 = 8, f(3) = 11, f(4) = 14, f(5) = 17, and f(6) = 20. Then we can take the average of the five numbers:

average = (8 + 11 + 14 + 17 + 20) / 5 = 14

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Question

Find the mean of the following numbers:

150, 88, 141, 110, 79

Answer

The mean is the average. The mean can be found by taking the sum of all the numbers (150 + 88 + 141 + 110 + 79 = 568) and then dividing the sum by how many numbers there are (5).

Our answer is 113 3/5, which can be written as a decimal.

Therefore 113 3/5 is equivalent to 113.6, which is our answer.

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Question

If you roll a fair die six million times, what is the average expected number that you roll?

Answer

The outcomes from rolling a die are {1,2,3,4,5,6}.

The mean is (1+2+3+4+5+6)/6 = 3.5.

Rolling the die six million times simply suggests that each number will appear approximately one million times. Since each number is rolled with equal probability, it doesn't matter how many times you perform the experiment; the answer will always remain the same.

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Question

Reginald has scores of {87, 79, 95, 91} on the first four exams in his Spanish class. What is the minimum score he must get on the fifth exam to get an A (90 or higher) for his final grade?

Answer

To find the fifth score, we need to set the average of all of the scores equal to 90.

Multiply both sides of the equation by 5.

Subtract 352 from both sides of equation.

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Question

The mean of the following set is 8. What is ?

Answer

Let .

We know the mean is 8, and there are five values in the set, including the unknown .

Simplify.

Plug back into equation at top.

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Question

If the mean of the following set is 12, what is ?

(1,14,3,15,16,,21,10)

Answer

Since we are given the mean, we need to find the sum of the numbers. From there we can figure out . We know

We can use this to find the sum by plugging in

So our sum is 96.

So we know that our total sum minus the sum of the given numbers is equal to .

So, .

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Question

The mean of the following numbers is 12. Solve for x.

14, 11, 10, 8, x

Answer

where n equals the number of events.

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Question

On four exams, John has an average score of 94 points. His lowest score was an 89. If this score is dropped, what is his new average?

Answer

To answer this question, you must first calculate John's total points from the four exams. The total points will be equal to four times the original average:

Now, if the 89 is removed, his new total will be:

With the score dropped, his new total number of exams is 3. Therefore, the new average is:

Round this up to 95.67.

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Question

After five exams, Isidore has an average score of 88 points. He then takes two more exams, earning a 77 and a 103. What is his new average?

Answer

To solve this, first calculate the total number of points that Isidore has earned. To find this total, multiply his original average by the original number of exams:

Then, to this you must add his new scores to get the new total:

After taking the two new exams, he has 7 total exams. Therefore, his average is:

This rounds to an 88.57.

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Question

Sally is five inches taller than Mike, who is three inches shorter than Patrick. Patrick is 67 inches tall. What is the mean height of the three people?

Answer

To calculate the mean, you will need to figure out each person's height. Start with what we know.

Patrick is 67 inches tall: .

Mike is three inches shorter than Patrick: .

Sally is five inches taller than Mike: .

Find the sum of their heights:

Their average height is therefore:

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Question

In a bed of plants, six are 55 inches tall, twelve are 70 inches tall, and three are 80 inches tall. To the nearest hundreth, what is the average height of the plants?

Answer

To answer this, you need to know the total inches of all the plants. You must multiply the number of each type by its respective height:

Then, add these together:

Now, the total number of plants is:

The mean (or average) of this group is:

Round this to the nearest hundreth to get 67.14 inches.

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Question

Peter was paid $4000 for editing a 3200-page encyclopedia. What was his rate earned per page?

Answer

This question is really just asking for the average dollar per page. This could be easily calculated:

However, you might also think of this as a rate problem:

Using the information from the question, we can see that and .

This comes out to what we solved above:

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Question

In a class, there are fifteen girls and thirty boys. The girls had an average height of 45 inches, and the boys had an average height of 45.5 inches. If the number of girls is doubled, but they maintain the same average height, what is the new average height of the class (to the nearest hundredth)?

Answer

To calculate this, you need to figure out the total number of inches in the classroom. This is calculated by multiplying each group by its average number of inches. For the girls, there will be 30 after they double. Their total number of inches can be found by multiplying the average height by 30:

The boys' total height can be found by multiplying their average by 30 as well:

There are now 60 students total, so the average number of inches is the combined height of the boys and girls divided by 60:

The averge height in the class is 45.25 inches.

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Question

A group of five candles are burning. Each candle is 1.5 inches taller than the one to its left. The smallest candle is 5 inches tall. What is the mean height of the group?

Answer

To solve this, you should first calculate the size of the candles. Based on the description, the group would be:

The sum of this group is:

The average is then found by dividing this total by 5:

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Question

A bank has 100 accounts established. The smallest account contains $1000. Each account after this one is $100 more than the one previous. For instance, the next account is $1100, then the next $1200, and so forth. What is the mean value of the accounts in the bank?

Answer

The easiest way to think of this problem is to make a list of the accounts (though not all 100, of course).

The largest account will be:

.

So, our list looks like this:

1000, 1100, 1200, . . ., 9700, 9800, 9900

Now we need to identify a pattern. We can pair the first and the last element:

Now, notice what happens when we pair the second and the second from the last element:

This pattern is going to work for the whole list! If there are 100 total accounts, that means that we can make 50 such pairs. That means that we have 50 pairs of $10900. The total account amount is therefore:

The mean will be equal to this total value divided by the number of accounts (100):

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Question

Find the mean of the following data set

Answer

The mean is the average of a set of data. In order to calculate this value, we need to take the sum of all the numbers and divide that by the number of values we have:

This gives us:

which finally gives us a mean of:

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Question

Angela scored the following on her past tests.

What is the current average (mean) score of her exams?

Answer

To find the average, add up all of the scores, then divide by how many scores there were:

.

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Question

The average score on a test that Sarah was absent for was . What must Sarah score on test to bring the average up to , if there are other students in the class?

Answer

Set equal to the sum of the tests of the first students.

Now set up an equation to solve for Sarah's test score:

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Question

In the Olympics gymnastics time trials, Sally's scores were . The highest score Sally can earn is a . Suppose she has one more opportunity to earn a qualifying score of to be on a team. Which of the following statements is TRUE?

Answer

In order to determine whether Sally will qualify for the last time trial, set up an equation to find the mean. Out of the five scores, one of the scores is unknown, and Sally's final score must be or higher. Let the unknown score be .

Write the equation to solve for the mean.

Unfortunately, Sally cannot make the gymnastics team because she needs to earn a 10.8, which is not possible on the score limit.

The correct answer is:

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Question

The average of the class on the most recent exam was an 84.1. The 2 lowest scores of the class were 71 and 73. If the teacher decides to removed the 2 lowest scores from the class average and there are 10 students in the class, what is the new class average?

Answer

To get the total combined score of everyone in the class, multiply the average of the class by the number of students.

. Since the teacher decided to drop the lowest 2 scores, let's subtract those 2 scores from the total.

.

Now the new total is 697. To find the new average, divide this new total by the new number of grades to be averaged in, which is 8. Remember that the teacher dropped 2 grades so there are less grades to take into account.

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