The first term of an AP is 5 and the last term is 57.If the
arithmetic progression consists of 20 terms, calculate the sum of all the
terms.

__Solution__

**A**

_{1}= 5, n=20, A_{n}= 57

**S**

_{n}=__n__(A_{1}+ A_{n})**2**

**S**

_{20}=__20__(5 + 57)**2**

**S**

_{20}= 10 x 62

**S**

_{20}= 620

*Hence the sum of all 23 terms is 620.*