if three arithmetic means areinserted between 11 and 39, find the second arithmetic mean
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Step-by-step explanation:
So the sequence is arithmetic …
Let the sequence be 11 a2 a3 a4 39.
Then a2=11+r, where r is the common difference.
a3=a2+r=11+2*r
a4=a3+r=11+3*r
a5=39=a4+r=11+4r =>r=(39–11)/4=7
So a2=11+7=18.
Therefore the second number in the arithmetic sequence is 18
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