Add the weights, then divide the sum by six:

$\displaystyle 145+172+166+159+153+201=996$

$\displaystyle 996 \div 6 = 166$

There are six elements, so to find the mean, add the elements and divide by six:

$\displaystyle \left ( 2+4+8+16+32+64 \right )\div 6 = 126 \div 6 = 21$

One ton is equal to 2,000 pounds.

The mean of the weights of the students is the total of their weights divided by the number of students.

Let $\displaystyle T$ be the total of their weights.

$\displaystyle 186 = T \div 11$

$\displaystyle T = 186 \cdot11 = 2,046 > 2,000$

(A) is greater.

You can find the average of a set of numbers by adding up the numbers and dividing by how many numbers are in the data set. Since David is trying to acheive an average of 85 by his fourth test, we should multiply 85 by 4.

$\displaystyle \text{average}=85=\frac{\text{total}}{4}$

$\displaystyle \text{total}=85\times4 = 340$

The result is the number that the four tests should total in order to achieve an average of 85. Then, add up the test scores Daid has recieved so far:

$\displaystyle 77 + 92 + 80 = 249$

If you subtract this number (the total from the test scores so far) from 340, the result will be the score needed to achieve the 85 average.

$\displaystyle 340 - 249 = 91$

David must score a 91 on his fourth test.

You can find the average of a set of numbers by adding up all the numbers in that set and dividing by how many numbers you added total. Here is a summary of our set:

Monday: 2 miles

Tuesday: 3 miles

Wednesday: 0 miles

Thursday: 3 miles

Friday: 2 miles

Keep in mind that we are looking for the average number of miles June ran Monday through Friday, and that there are 5 days in that period. You must also account for the 0 miles that June ran on Wednesday. 

$\displaystyle \text{average}=\frac{\text{total miles}}{\text{total days}}=\frac{2+3+0+3+2}{5}=\frac{10}{5}$

June ran a total of 10 miles during that 5 day period. You must then divide by the number of days in order to get the average.

$\displaystyle 10 \div 5 = 2$

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 $\displaystyle 60/5 = 12$.

Add the six elements and divide the sum by 6:

$\displaystyle 56 + 78 + 98 + 85 +77 + 73 = 467$

$\displaystyle 467 \div 6 \approx 77.8$

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.

Divide the sum of the scores by eight:

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

Divide the sum of the scores by nine:

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