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The sum of the first $N$ positive odd numbers is 121. What is the value of $N$?

 Aug 20, 2019
 #1
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Note  that  the sum of the first  four odd positive integers  =   1  +  3  +  5  + 7    =  16 =     4^2  

 

So....the sum of the first N positive  odd integers  =  N^2

 

So

 

N^2  =121     take the square root

 

N  = 11

 

 

cool cool cool

 Aug 20, 2019
edited by CPhill  Aug 21, 2019
edited by CPhill  Aug 21, 2019
 #2
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thanks i didn't know about the sum of the consecutive odd numbers were squared. 

Guest Aug 21, 2019

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