Answers

2016-06-09T21:27:56+08:00
  3 arithmetic means are inserted between  11 & 39

       to find the common difference   d    follow the pattern below
   
   first step :             39-11 =  28
     to find    d    =     28/n-1         
                         =   28/4        /  n = 5,   there are five terms
                         =       7
      so the arithmetic sequence is:     11,18,25,32,39
         the second arithmetic mean  is     25


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you are right again, the second arithmetic mean should be 25 thanks so much