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How many terms of the sequence7,11,15...,starting from the first,must be added to get 592?
Given that Sn = 592
                   a  = 7
                  d   = 4 
    We have Sn = n/2[2a + (n-1)d]
                592 =   n/2[14 + (n-1)4] 
                592 = n[7 + (n-1)2]
ie,            2n2 + 5n - 592 = 0
              By solving this equation we get, n = 32
So there are 32 terms.
            


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