Question

In an Arithmetic progression, the first term $a=10$, and last term, $l=100$. The number of terms is $1000$. Find their sum.

• A. $52,000$
• B. $53,000$
• C. $54,000$
• D. $55,000$

Answer 1

The correct option is D $55,000$

Given, $a=10,\text{last term}=100$ and $\text{number of terms}=1000$

Sum of first $n$ terms in an A.P. is
$S_n=\frac{n}{2}$ [First term $+$ Last term]
$=\frac{1000}{2}[10+100]$
$=500\left[110\right]$
$S_{1000}=55,000$