# Thread: Summation notation

1. ## Summation notation

Question. Does anyone have an answer? I'm stumped on these. Thank you

2. Originally Posted by Y-rag
Question. Does anyone have an answer? I'm stumped on these. Thank you
What is the value of each $\displaystyle x_i~?$

3. The following is a list of 13 measurements:

Suppose that these 13 measurements are respectively labeled . (Thus, is labeled , is labeled , and so on.) Does that help? I'm clueless to these.

4. The way that you ahve this thing written calls for more information necessary to find the solution. What your statement makes is that there are 13 values of x that need to be added together and then divided by 11. But, those values of x are still a mystery. They could be anything. All we know is that there are 13 of them.

here's what it looks like

$\displaystyle \sum_{i=1}^{13}\frac{x_i}{11}=\frac{x_1+x_2+x_3+x_ 4+x_5+x_6+x_7+x_8+x_9+x_{10}+x_{11}+x_{12}+x_{13}} {11}$

If however you meant to say

$\displaystyle \sum_{i=1}^{13}\frac{i}{11}$

That's different and it looks like this

$\displaystyle \sum_{i=1}^{13}\frac{i}{11}=\frac{1+2+3+4+5+6+7+8+ 9+10+11+12+13}{11}$

So, whichever way you meant to write this thing, hopefully I've helped you.

5. Well, that helps a bunch! Just take a look at what I've got wrriten. All you gotta do is add all those measurements up and divide by 11!

6. $\displaystyle \frac{70+(-40)+....}{11}$

7. The following is a list of 13 measurements:
73, -40, 99, -16, 19, 89, 65, 10, 88, 46, -30, -18, -43

Suppose that these 13 measurements are respectively labeled . (Thus, is labeled , is labeled , and so on.)
Find . Round your answer to at least two decimal places.

#1. Sorry I didn't give you all the info req'd.
#2. I went out to mow the lawn and get some sanity back.

Thank you very much for your help.

Gary

8. ## Help

If I had 12 measurements: 30, -38, -70, -78, 32, 73, 49, -88, 29, 32, 42, 6, and they were labeled x1, x2, x3 etc, how would I find the following?

Find .

I added all the numbers, and came up w/19. Then I took x1 which was 30 and added 49 to that and then multiplied that by 19 and came up w/1501 which is the wrong answer. Can anybody help me w/this? Thank you.

### Suppose that these 13 measurements are respectively labeled x1 , x2 , ... , x13 . (Thus, 83 is labeled x1 , −55 is labeled x2 , and so on.) Compute the following.

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