Question

The sum of $n$ terms of an A.P. can be calculated using which of the following

• A. $S_n=n/2[a-(n-1\left)d\right].$
• B. $S_n=n/2[2a+(n-1\left)d\right].$
• C. $S_n=n/2[a+(n-1\left)d\right].$
• D. $S_n=n[2a+(n-1\left)d\right].$

Answer 1

Answer: (B)

$S_n=n/2[2a+(n-1\left)d\right].$

The sum of $n$ terms of an arithmetic progression is given by $Sn=n/2[2a+(n-1\left)d\right]$ where a is the first term, $d$ is the common difference and $n$ is the number of terms in the arithmetic progression. Thus the correct answer is $b$.