Question

Calculate the sum of natural numbers between $1$ and $42$.

• A. $460$
• B. $900$
• C. $903$
• D. $920$

Answer 1

Answer: (C)

$903$

The sum of first $n$ terms of arithmetic series formula can be written as,
$S_n=\frac{n}{2}[2a+(n-1\left)d\right]$ ............ (1)

First Term: $a=1$

Last term: $b=42$

Summation of series: $\frac{n}{2}(a+b)$

$1+2+3+...+42=\frac{42}{2}(1+42)=21\times 43=903$