Common Core: 6th Grade Math : Find mean

Study concepts, example questions & explanations for Common Core: 6th Grade Math

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Example Questions

Example Question #1 : Find Mean

In a group of 4 books, the average number of pages is is 10.  Juan adds a book with 20 pages to the group.  What is the new average number of pages?

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 12\)

\(\displaystyle 30\)

\(\displaystyle 20\)

\(\displaystyle 15\)

Correct answer:

\(\displaystyle 12\)

Explanation:

If the average of 4 books was 10, then the total number of pages was \(\displaystyle 4\times10 =40\). Adding in the 20 new pages, but now dividing by 5 you get \(\displaystyle 60/5 = 12\).

Example Question #1 : Find Mean

Give the mean of the data set (nearest tenth, if applicable): 

\(\displaystyle \left \{ 56,78,98,85,77,73 \right \}\)

Possible Answers:

\(\displaystyle 77.8\)

\(\displaystyle 76.5\)

\(\displaystyle 75.7\)

\(\displaystyle 79.6\)

\(\displaystyle 77.3\)

Correct answer:

\(\displaystyle 77.8\)

Explanation:

Add the six elements and divide the sum by 6:

\(\displaystyle 56 + 78 + 98 + 85 +77 + 73 = 467\)

\(\displaystyle 467 \div 6 \approx 77.8\)

Example Question #2 : Find Mean

Find the mean of this set of numbers:

54, 41, 99, 120, 66.

Possible Answers:

\(\displaystyle 79\)

\(\displaystyle 99\)

\(\displaystyle 80\)

\(\displaystyle 76\)

Correct answer:

\(\displaystyle 76\)

Explanation:

Firrst, add the numbers:

\(\displaystyle 54+41+99+120+66=380\)

Then, divide by the amount of numbers in the set:

\(\displaystyle 380\div 5=76\)

Answer: The mean is 76.

Example Question #3 : Find Mean

Give the mean of the following eight scores: 

\(\displaystyle \left \{ 61, 67, 80, 72, 76, 73, 90, 68 \right \}\)

Possible Answers:

\(\displaystyle 72.875\)

\(\displaystyle 73.375\)

\(\displaystyle 72.5\)

\(\displaystyle 73\)

\(\displaystyle 75.5\)

Correct answer:

\(\displaystyle 73.375\)

Explanation:

Divide the sum of the scores by eight:

\(\displaystyle \frac{ 61+ 67+80+72+76+73+90+ 68}{8} = \frac{ 587}{8} = 73.375\)

Example Question #1 : Data Analysis

Give the mean of the following nine scores: 

\(\displaystyle \left \{ 61, 67, 80, 72, 76, 73, 90, 68, 70 \right \}\)

Possible Answers:

\(\displaystyle 75.5\)

\(\displaystyle 72\)

\(\displaystyle 73\)

\(\displaystyle 68\)

\(\displaystyle 72.5\)

Correct answer:

\(\displaystyle 73\)

Explanation:

Divide the sum of the scores by nine:

\(\displaystyle \frac{ 61 + 67+ 80+ 72+ 76+73+90+68+70}{9} = \frac{ 657}{9} = 73\)

Example Question #2 : Data Analysis

The average age of 4 people is 12.  What will be the sum of their ages in 3 years?

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 56\)

\(\displaystyle 60\)

\(\displaystyle 15\)

\(\displaystyle 24\)

Correct answer:

\(\displaystyle 60\)

Explanation:

The current sum of their ages is \(\displaystyle 12\times 4=48\).  Since all 4 people will gain 3 years in age, we have to add 12 to the current sum.

Example Question #2 : Find Mean

Give the mean of the following data set:

\(\displaystyle \left \{1, 2, 3, 3, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 9, 10 \right \}\)

Possible Answers:

\(\displaystyle 5\)

\(\displaystyle 5.0625\)

\(\displaystyle 5.375\)

\(\displaystyle 6\)

\(\displaystyle 5.5\)

Correct answer:

\(\displaystyle 5.0625\)

Explanation:

Since there are 16 elements, divide their sum by 16 to get the mean:

\(\displaystyle (1+ 2+ 3+ 3+ 4+ 4+ 4+ 5+ 5+ 6+ 6+ 6+ 6+ 7+ 9+ 10) \div 16 = 81 \div 16 = 5.0625\)

Example Question #1 : Find Mean

Find the average of this set of numbers:

521, 834, 754, 902, 899

Possible Answers:

\(\displaystyle 782\)

\(\displaystyle 600\)

\(\displaystyle 378\)

\(\displaystyle 754\)

Correct answer:

\(\displaystyle 782\)

Explanation:

First, add all the numbers in this set:

\(\displaystyle 521+834+754+902+899=3910\)

Divide, 3910 by the total amount of numbers in the set:

\(\displaystyle 3910\div 5=782\)

Answer: The average is 782.

Example Question #4 : Find Mean

Find the mean in this set of numbers:

5570, 4886, 5226, 4120, 6561, 4120, 6008

Possible Answers:

\(\displaystyle 2440\)

\(\displaystyle 5213\)

\(\displaystyle 5226\)

\(\displaystyle 4120\)

Correct answer:

\(\displaystyle 5213\)

Explanation:

First, add all the numbers in this set:

\(\displaystyle 5570+4886+5226+4120+6561+4120+6008=36491\)

Then, divide that amount by the total number in the set:

\(\displaystyle 36491\div 7=5213\)

 

Answer: The mean is 5213.

Example Question #3 : Find Mean

Find the average of this set of numbers:

2521, 2512, 2525, 2552, 2551, 2525, 2517

Possible Answers:

\(\displaystyle 2552\)

\(\displaystyle 2525\)

\(\displaystyle 40\)

\(\displaystyle 2529\)

Correct answer:

\(\displaystyle 2529\)

Explanation:

First, add all the numbers in this set:

\(\displaystyle 2521+ 2512+2525+2552+2551+2525+2517=17703\)

Then, divide by the amount of numbers in the set:

\(\displaystyle 17703\div 7=2529\)

Answer: The average is \(\displaystyle 2529.\)

 

 

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