For the life of me I can't figure out how to express this. Basically it starts with 15 then adds 9 the next round, then 8, then 7, etc. Basically diminishes by 1 each round until it hits zero. How would I write this formula? Any help would be much appreciated!
Trying to figure out how to write this formula.
- Thread starter Stingraey
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pka
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Because \(\displaystyle 9 + 8 + 7 + \cdots + 1 = 1 + 2 + \cdots + 9 = \sum\limits_{k = 0}^9 k \), it is simply \(\displaystyle 15+ \sum\limits_{k = 0}^9 k \).
HallsofIvy
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I'm not sure what you mean by a "round". Is it important to keep the rounds in order?
If not, I would just note that the "odd" one is that "15" and separate it from the others: 15+ (9+ 8+ 7+ 6+ 5+ 4+ 3+ 2 +1). Now you could either just add 9+ 8+ 7+ 6+ 5+ 4+ 3+ 2+ 1= 45 so see that is 15+ 45= 60. Or you could use the fact that the "average" value of a arithmetic sequence is the same as the average of the highest and lowest numbers. The average of 9 and 1 is 10/2= 5 so this sum of 9 numbers is the same same as 9(5)= 45 and then 15+ 45= 60.
Or if you are asking about "running sum", it is \(\displaystyle 15+ \sum_{i=1}^n 10- i\).
If not, I would just note that the "odd" one is that "15" and separate it from the others: 15+ (9+ 8+ 7+ 6+ 5+ 4+ 3+ 2 +1). Now you could either just add 9+ 8+ 7+ 6+ 5+ 4+ 3+ 2+ 1= 45 so see that is 15+ 45= 60. Or you could use the fact that the "average" value of a arithmetic sequence is the same as the average of the highest and lowest numbers. The average of 9 and 1 is 10/2= 5 so this sum of 9 numbers is the same same as 9(5)= 45 and then 15+ 45= 60.
Or if you are asking about "running sum", it is \(\displaystyle 15+ \sum_{i=1}^n 10- i\).
D
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Formula for what?
last number 15, 24, 32, 39, 45, 50, 54, 57, 59, 60, 60......
Or sum of those numbers? S = 15 + 24 + 32 + 39 + 45 + 50 + 54 + 57 + 59 + 60 + 60
Or something else like pka suggested!
Please share your work with us .
If you are stuck at the beginning tell us and we'll start with the definitions such as "what is commisson"?"
You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL:
http://www.freemathhelp.com/forum/th...217#post322217
Basically x = round
So when x=1 the value is 15, x = 2 is 24, then 32, 39, etc. Just want to know how you would write that formula. So I can just plug the round # in where X is and determine the value without having to add the 9 then the 8 then the 7 all over again. Thanks for all your responses btw!
So when x=1 the value is 15, x = 2 is 24, then 32, 39, etc. Just want to know how you would write that formula. So I can just plug the round # in where X is and determine the value without having to add the 9 then the 8 then the 7 all over again. Thanks for all your responses btw!
What i'm after is the FORMULA. Not any particular number.
So if the number of rounds is 3 for example (X=3). I can just plug in a 3 where the X is in the formula and determine what the value is. Which in this case would be 32(15, +9, +8). However, this isnt a one and done deal. It's going to be used many many times. I'm only looking for the formula.
So if the number of rounds is 3 for example (X=3). I can just plug in a 3 where the X is in the formula and determine what the value is. Which in this case would be 32(15, +9, +8). However, this isnt a one and done deal. It's going to be used many many times. I'm only looking for the formula.
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