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 January 14th, 2013, 04:00 AM #1 Member   Joined: Jan 2013 Posts: 93 Thanks: 0 sum of the first 50 terms Determine the sum of the first 50 terms in the series 1+(1/2)+(1/2)^2 +(1/2)^3 +..... I actually already answered this question but would like to get confirmation on it! I used formula: Sn=(a1+an)/2 n After futher calculations: an=a1+(n-1) r , r=1/2, a50=? a50= 51/2 And then using main formula S50= 1325/2=662.5 Am i correct? January 14th, 2013, 05:06 AM #2 Global Moderator   Joined: Nov 2006 From: UTC -5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms Re: sum of the first 50 terms The sum should be bounded above by 2, right? January 14th, 2013, 05:17 AM #3 Member   Joined: Jan 2013 Posts: 93 Thanks: 0 Re: sum of the first 50 terms Yes, but i thought i already did that. S50= ((1+25.5)/ 2)* 50= 53/2 *25= 1325/2= 662.5 January 14th, 2013, 05:59 AM   #4
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Re: sum of the first 50 terms

Hello, Agata78!

Quote:

[color=beige]n . . . . .[/color] January 14th, 2013, 06:12 AM   #5
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Re: sum of the first 50 terms

Quote:
 Originally Posted by Agata78 Yes, but i thought i already did that. S50= ((1+25.5)/ 2)* 50= 53/2 *25= 1325/2= 662.5
662.5 > 2, so this clearly can't be the answer. soroban has the right idea, above. January 14th, 2013, 06:15 AM #6 Member   Joined: Jan 2013 Posts: 93 Thanks: 0 Re: sum of the first 50 terms I have completely different formula. But i think yours makes more sense then mine! Thank you Tags sum, terms Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post stevecowall Algebra 8 February 28th, 2012 12:59 PM stevecowall Algebra 1 February 17th, 2012 06:53 PM jazzycafe Algebra 6 November 18th, 2009 05:58 PM riponks Elementary Math 5 September 24th, 2009 03:50 AM Soha Algebra 4 December 19th, 2006 04:23 PM

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