Answers

2016-07-03T17:25:11+08:00
An=a1 +(n-1)d
a2=11+(n-1)d
39=11+(2-1)d
39=11+1d
39-11=1d
28=1d
28/1=1d/1
d=28
answer is, 28 is the second arithmetic mean,
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