Mean - GRE Subject Test: Math

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Question

Find the mean of the following set of numbers:

Answer

The mean can be found in the same way as the average of a group of numbers. To find the average, use the following formula:

So, if our set consists of

We will get our mean via:

So our answer is

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Question

Find the mean.

Answer

To find the mean, add the terms up and divide by the number of terms.

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Question

Find if the mean of is .

Answer

To find the mean, add the terms up and divide by the number of terms.

Then add the numerator.

Cross-multiply.

Subtract on both sides.

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Question

If average of and is and is what is the average of ?

Answer

If the average of and is , then the sum must be .

If we add the sum of we get or .

To find the average of the three terms, we divide and to get .

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Question

What is the average of the first ten prime numbers?

Answer

The first ten prime numbers are . Prime numbers have two factors: and the number itself. Then to find mean, we add all the numbers and divide by .

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Question

If the average of seven consecutive numbers is , what is the value of the second number in the set?

Answer

There are two methods.

Method 1:

Since the average of consecutive number is , we can express this as:

Cross-multiply

Subtract on both sides then divide both sides by

Since we are looking for the second term, just plug into expression . That means answer is or .

Method 2:

Since the average of consecutive number is , this means the median is also . Consecutive means one after another and with each term having the same difference, we know the mean equals the median. Since there are terms, the median will have terms left and right of it. Then, the series will go . The second term is .

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Question

John has math test scores of . What could be his final test score if he wants the average of his exams to be at least ?

Answer

To find the missing value, we add the terms up and divide them by to have the average of .

Cross-multiply.

Subtract both sides by

Since the question is asking for a test score that will generate AT LEAST average of , we look for an answer that is greater than which is .

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Question

The mean of four numbers is .

A: The sum of the four numbers.

B:

Answer

To find the sum of the four numbers, just multiply four and the average. By multiplying the average and number of terms, we get the sum of the four numbers regardless of what those values could be.

Since Quantity A matches Quantity B, answer should be both are equal.

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Question

Mean of is . are all positive integers. is between and inclusive.

A: Mean of .

B: Mean of .

Answer

Let's look at a case where .

Let's have be and be . The sum of the three numbers have to be or .

The average of is or . The avergae of is or .

This makes Quantity B bigger, HOWEVER, what if we switched the and values.

The average of is still or . The avergae of is or .

This makes Quantity A bigger. Because we have two different scenarios, this makes the answer can't be determined based on the information above.

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Question

Sam has math test scores of . The teacher drops the lowest test score except the final and the highest test score is counted as two exams. If Sam took his final exam and felt he scored between inclusive, what is the lowest possible average of his exams?

Answer

We have four test scores of . We know the range of the final exam is so therefore the is counted twice. Since the final exam grade regardless if the lowest possible value can't be dropped, this means we drop the and include the lowest possible test score which is . So the mean is:

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Question

If and are positive integers from inclusive, then:

A: The mean of

B: The mean of

Answer

Let's add each expression from each respective quantity

Quantity A:

Quantity B:

Since we will let and . The sum of Quantity A is and the sum of Quantity B is also . HOWEVER, if was , that means the sum mof Quantity B is . With the same number of terms in both quantities, the larger sum means greater mean. First scenario, we would have same mean but the next scenario we have Quantity B with a greater mean. The answer is can't be determined from the information above.

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Question

John picks five numbers out of a set of seven and decides to find the average. The set has .

A: John averages the five numbers he picked from the set.

B:

Answer

To figure out which Quantity is greater, let's find the highest possible mean in Quantity A. We should pick the biggest numbers which are . The mean is . This is the highest possible mean and since Quantity B is this makes Quantity B is greater the correct answer.

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Question

There were exams graded. The average of the exams were . If the average of exams were , what was the average of the remaining exams?

Answer

With exams of average , the sum of the scores were .

We already know the first exams with average of . Therefore, the sum is .

The remaining number of exams is or .

The remaining sum is or .

We divide by to get .

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Question

What is the mean of the scores 95, 13, 67, 89, 13, 45, and 109?

Answer

To get the average or mean, add up all the scores and then divide by the number of scores.

There are seven scores so divide that number by 7

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Question

Find the mean of the set of numbers containing: .

Answer

Step 1: We need to know how to find mean. To find mean, add up all the numbers in the set and divide by how many numbers are in the set.

Step 2: Let's find the sum:

.

Step 3: Count how many numbers are in the set.

..There are 9 numbers.

Step 4: Divide the sum by 9 to find the average.

.

The average of the set of numbers is

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Question

What is the mean of ?

Answer

Step 1: Find the sum of all the numbers.

Step 2: Divide the sum by how many numbers there are. There are 11 numbers.

The mean (average) of all numbers above is .

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Question

What is the mean of

Answer

Step 1: Find the sum of all the numbers:

Step 2: Divide the sum by how many numbers are given to get the mean..

There are numbers...

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Question

What is the mean of ?

Answer

Step 1: Find the sum of all numbers:

Step 2: Count how many numbers are in the question..

We have numbers.

Step 3: Divide sum by how many numbers

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Question

What is the mean of

Answer

Step 1: Find the sum of the numbers

Step 2: Find how many numbers

There are numbers..

Step 3: Divide the sum by how many numbers they are...This division gives us the mean..

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Question

What is the mean of:

Answer

Step 1: Find the sum of the numbers

Step 2: Find how many numbers are there

I counted numbers.

Step 3: Divide Sum by how many numbers

The mean is .

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