SOLUTION: If the 6th term of an AP IS 121,find the sum of the first 11 terms

Question 1037860: If the 6th term of an AP IS 121,find the sum of the first 11 terms

Answer by ikleyn(52810) (Show Source): You can put this solution on YOUR website!
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If the 6th term of an AP IS 121,find the sum of the first 11 terms
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We can write 

  = ,    = ,

  = ,   = ,

  = ,   = ,

 = ,   = ,

 = ,   = .


Then 

 = .

Add , and you will get that the sum of the first 11 terms is equal to .

Hence, this sum is 11*21 = 231.

Answer.  231.

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