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![]() Assume that 10 numbers = 200 What formula would I use to average (weight) these 10 numbers so that the 2nd number is 10% greater than the 1st, the 3rd number is 10% greater than the 2nd, the 4th number is 10% greater than the 3rd, etc . . . and the total of 10 numbers will equal 200? Im sure someone knows the answer! Thanx in advance Kevin -- Kevin |
#2
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Not sure why you use the terms 'weight' and 'average' so I may have missed
the point You seem to be talking about a geometric series a + ar + ar² + ar³ ...... ar^(n-1) In your case r = 1.1 (a 10% increase each time) and n=9 (you have 10 numbers) You could look at http://en.wikipedia.org/wiki/Geometric_series and do some algebra But I put 1 in A1 In A1 I use =A1*1.1 This I copied down to A10 In A11 I used =SUM(A1:A10) Then I used Solver to make A11 equal 200 by changing A1; it gave an answer of 12.5490789765023 I also used Goal Seek and it gave the same result (of course) best wishes -- Bernard V Liengme Microsoft Excel MVP http://people.stfx.ca/bliengme remove caps from email "Kevin" wrote in message ... Assume that 10 numbers = 200 What formula would I use to average (weight) these 10 numbers so that the 2nd number is 10% greater than the 1st, the 3rd number is 10% greater than the 2nd, the 4th number is 10% greater than the 3rd, etc . . . and the total of 10 numbers will equal 200? I'm sure someone knows the answer! Thanx in advance Kevin -- Kevin |
#3
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What formula would I use to average (weight) these 10 numbers so that
the 2nd number is 10% greater than the 1st, the 3rd number is 10% greater than the 2nd, the 4th number is 10% greater than the 3rd, etc . . . and the total of 10 numbers will equal 200? Here's one way, starting with a new worksheet. In A2, put =A1*1.1 Select A2 and extend down to A10 In A11 put =SUM(A1:A10) Here comes the interesting part, where we get a total of 200. Use Tools Goal seek and in the dialog box that this brings up, put Set cell: A11 To value: 200 By changing: A1 Click "OK" and "OK" The result is in A1:A10. |
#4
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As the first number, use
=200/SUM(1.1^(ROW(A1:A10)-1)) Entered using Ctrl-Shift-Enter HTH, Bernie "Kevin" wrote in message ... Assume that 10 numbers = 200 What formula would I use to average (weight) these 10 numbers so that the 2nd number is 10% greater than the 1st, the 3rd number is 10% greater than the 2nd, the 4th number is 10% greater than the 3rd, etc . . . and the total of 10 numbers will equal 200? Im sure someone knows the answer! Thanx in advance Kevin -- Kevin |
#5
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Hello Bernard,
... In your case r = 1.1 (a 10% increase each time) and n=9 (you have 10 ... n=10 (you have 10 numbers) but highest exponent is 9 (=10 - 1) SCNR, Bernd |
#6
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Your are right - I realized this as I dropped of the sleep last night!
cheers -- Bernard "Bernd P" wrote in message ... Hello Bernard, ... In your case r = 1.1 (a 10% increase each time) and n=9 (you have 10 ... n=10 (you have 10 numbers) but highest exponent is 9 (=10 - 1) SCNR, Bernd |
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