**Find the sum of the 1st 16 terms of the following arithmetic progression: 5+11+17+…………………**

__Solution__

**d=6, A**

_{1}= 5,n=16

**S**

_{n}=__n__[2A_{1}+ (n-1)d]**2**

**S**

_{16}=__16__[2(5) + (16-1)d]**2**

**S**

_{16}= 8[10 + 15d]

**S**

_{16}= 8[10 + 15(6)] since d=6**S**

_{16}= 8[10 + 90]

**S**

_{16}= 8 x 100

**S**

_{16}=**800**

**Therefore the sum of 1st 16 terms is 800.**

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**Find the sum of the 1st 16 terms of the following arithmetic progression: 6+14+22+…………………**

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