Question

The value of $\sum 18+\sum 19$ is

• A. $324$
• B. $361$
• C. $703$
• D. $743$

Answer 1

Answer: (B)

$361$

To find:

$\sum 18+\sum 19=?$

Solution:

We know that $\sum n=\frac{n(n+1)}{2}$

So, $\sum 18=\frac{18(18+1)}{2}$

$\sum 18=9\times 19=171$

Similarly,

$\sum 19=\frac{19(19+1)}{2}$

$\sum 19=19\times 10=190$

$\sum 18+\sum 19=171+190=361$

Therefore, $B$ is the correct option.